nr1en2012

SUMMARY

Ştefan IONICĂ, Cristian MĂRUNŢEANU Research to quantify the lignite extraction potential according to benches and bench system slope angles for open pit mines in Oltenia

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Dumitru IACOB The maintenance study of coal loading machine from Turceni power station’s coalyard

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Monica ANDREI Modification of the state of stresses and strains around the cavities resulted after the exploitation of salt by dissolution. Case study: Ocnele Mari exploitation

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Nicolae Daniel FÎŢĂ, Dragoş PĂSCULESCU, Lucian FÎŢĂ, Lucian DIODIU Organigram of upgrading and optimization power stations at high voltage, very high voltage and ultra high voltage

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Ioan-Liviu PIPIRIGĂ Anthropogenic activities from the Motru mining basin triggering emergencies

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William Flavy RITZIU Seismic response by spectral analysis of the system rock - underground construction (tunnel)

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Nicolae PĂUNESCU Landslides and slope collapse in the acumulation lake zone Gura Apelor

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Mihaela PAGNEJER 3D geotechnical model for the north-west area of Bucharest

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Mihai BOLGAR Geo-mechanical characterization of the A3 motorway route Comarnic-Predeal in the choice of tunneling technology execution with explosives

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RESEARCH TO QUANTIFY THE LIGNITE EXTRACTION POTENTIAL ACCORDING TO BENCHES AND BENCH SYSTEM SLOPE ANGLES FOR OPEN PIT MINES IN OLTENIA Ştefan IONICĂ*, Cristian MĂRUNŢEANU** Abstract In the lignite mining activities in open pit mines, the recovery of larger quantities of coal is based usually on "the temptation to force the slope angles" of the benches and bench systems. An important element to take this decision is the knowledge of the amount of coal that can be recovered.

1. Introduction One of the main conditions to improve the efficiency of lignite extraction by re-designing benches and bench system slope angles is the exact knowledge of the quantity of coal (tons) that can be capitalized at a time. Knowing the exact amount of coal that can be recovered is in fact the main key in the relationship "economic efficiency - safety

factor", i.e. both a larger quantity of exploited coal in a shorter time, and fulfilled stability conditions.

2. Coal extraction potential for working benches Passive reserve definition. According to the Figure 1 the "active reserve" is defined as the quantity of coal currently operated under the conditions of the designed angle "u1" to a certain career, and "passive reserve" as the quantity of coal that could be additional extracted in the case of an angle "u2", larger than u1, but satisfying the stability conditions.

In order to establish the "passive reserve" we count on the fact that the usually height of the working benches varies between 5.0 m and 20.0 m, the bench slope angle is usually 450 and the minimum thickness of a coal layer must be 1.0 m (condition imposed by the extraction equipment).

Fig. 1 – Working bench "Active reserve" / "passive reserve"

Construction of the mathematical model. The model, scaled 1 : 1, was realized by AutoCAD and defined for a bench 20.0 m height. The reference system of coordinates was chosen on the top of the bench. Thus, the model reference system is suitable for all benches less than 20.0 m height, respectively for any bench multiple of 1.0 m height in the interval [1.0, 20.0] m. ____________________________________ * Ph.D. stud. eng.- University of Bucureşti, Faculty of Geology and Geophysics ** Ph.D Prof.eng.- University of Bucureşti, Faculty of Geology and Geophysics Revista Minelor - Mining Revue no. 1 / 2012

Figure 2 presents in detail the model having on the vertical axis the bench height and the position of a coal layer 1.0 m height and on the horizontal axis the variation of the slope angle (from 450 to 800).

The interval of 50 of the slope angle was chosen thus to have both economic (amount of coal) and "practical" (values of the angle that can be worked by mining) relevance.

Therewith, for practical use of this model, the variation intervals were defined using the "chess board" principle.

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Fig. 2 – Working bench Mathematical model of "passive reserve" determination

3. Results Considering the coal layers perfectly horizontal (as shown in the Figure 2), the areas of the parallelograms drawn by the coal layers lines and the slope angles lines were determined by AutoCAD. The resulting “passive reserve” (in tons) for the model set is presented graphically in the Figure 4 for different slopes height and angle and for an average volumetric weight of coal of 12.5 kN / m3.

4. Coal extraction potential for final bench systems For an accurate assessment of the quantity of coal to be over-extracted in the case of designing of new

general slope of the bench system, we proposed an “ideal” bench system consisting on four benches.

Each bench is 20.0 m height and the slope angle 300. The general angle of the bench system is 80.

The “passive reserve” (hachured zones) has been calculated in the case of increasing of the slope angle from 80 to 150. In figure 3 the hachures represent the "passive reserve" by increasing the slope angle in the interval 80-100.

It is noted that the "passive reserve" together with the width of the benches increase from the upper part to the lower part of the bench system of the open pit mine.

Fig. 3 – Bench systemMathematical determination of the "passive reserve”

5. Conclusions By re-designing the slope angles of the working benches, considering an average volumetric weight of coal, additional amounts of coal can be extracted (tens of tons per linear meter of bench).

Re-designing the slope angles of the bench system (final slope) leads as well to the recovering

of important amounts of coal (thousands of tons per linear meter of slope). The recovered amount of coal by re-designing the general angle of the open pit mine is much more important than the amount of coal recovered by re-designing of the slope angle of the final individual benches.

In this direction, a special attention should be given to develop this extraction potential.

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Fig. 4 – Working bench. „Passive reserve” for different slope heights and angles

Fig. 5 – Bench system. „Passive reserve” for different bench and bench system slope angles

References 1. Ionică, Şt.

Research to increase the efficiency of lignite extraction by re-designing the geometric elements of working and final bench slopes in open pit mines, Ph.D thesys, 2011 2. SNLO Tg. Jiu, EMC Jilț, ICSITPML Craiova Technical reports

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THE MAINTENANCE STUDY OF COAL LOADING MACHINE FROM TURCENI POWER STATION’S COALYARD Dumitru IACOB* Abstract: This paper aims at studying the maintenance of machine type T2052 used for taking the coal in Turceni power station's coalyard. After a brief presentation of the machine construction is analysed its functionality, by highlighting the frequency of continuously failures, the sub-assemblies which go to accidental down-time through failure. Analysis shows that the superstructure's rotating system is most commonly exposed to damage. The maintenance study of this system shows that it is necessary to adopt preventivemaintenance strategy planned in order to avoid the occurrence of defects.

Cuvinte cheie: coalyard, loading machine, failure, rotating system, maintenance function, service intensity, preventive maintenance 1. Introduction After unloading the railway wagons, inside the power station, the coal (lignite) is taken over by six loading machines with short arm, type T 2052, and delivered to the coalyards, either directly for use in thermal power station.

Figure 1 shows the overall solution of the T 2052 type loading machine, whence result the main

parts of it.

The meaning of the numbers shown in the picture is: 1 - displacement gear from the railway ; 2 - rotation gear of the upper side with bucket wheel towards the groundwork; 3 - lever arm for rotor and conveyer; 4 - bucket wheel for loading the coal; 5 - belt conveyer from the arm where the bucket wheel put the coal on and which transport and discharge the coal on the high capacity belt from the discharging front; 6 - metallic tower 7 arm lift mechanism made by pulley, cables and sheaves; 8 - reverse arm for balancing the ballast box; 9 - electrical equipment of force and command.

The loading machine has the processing capacity of 1200 t/h.

2. Action of loading machine during exploitation Analyses of loading machine’s action has been made by using the information recorded in an year by watching ten machines of this kind in operation to Turceni coalyards.

This information are shown in table 1 and 2, figures 2-9, where are highlighted the numbers of failures, their causes and time of parking, which is actually the time used for repair.

Fig. 1 Overall view of loading machine T 2052 type used for loading the coal from power station’s discharge front

_____________________________ * Eng. – S.C. Complexul Energetic Turceni S.A. Revista Minelor - Mining Revue no. 1 / 2012

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Table 1. Failures and time of parking for loading machines type T 2052

No..

1 2 3 4 5 6 7 8 9 10

Loading machine Mp 1A Mp 1B Mp 2A Mp 2B Mp 4B Mp 5A Mp 10A Mp 10B Mp 26A Mp 26 B TOTAL

Number of failures Time or repair % from total item hours % from total 3 7,50 5 2,63 6 15,00 35 18,42 4 10,00 11 5,79 9 22,50 46 24,21 3 7,50 14 7,37 6 15,00 47 24,74 1 2,50 4 2,11 2 5,00 7 3,68 3 7,50 9 4,74 3 7,50 12 6,32 40 190

Table 2. Failures and time for repair ordered on subassembly Number of failures Time for repair No..

Faulty subassembly % from item % from total hours total Rotating system ( actuator set, mainly the conical-cylindric decelerator, 1 17 42,50 83 43,68 crown gear, assembler clutches) Belt conveyer ( vulcanization, belt joint, mat replacement, idler, fluid 2 8 20,00 58 30,53 coupling) 3 Displacement system on railway ( electrical engine, bogie) 9 22,50 32 16,84 4 Bucket wheel (electrical engine, decelerator, fluid coupling) 3 7,50 14 7,37 5 Lighting 3 7,50 3 1,58 TOTAL 40 190

Fig. 2 Order of failures for loading machines

Fig. 4 Order of repairing time for loading machines Revista Minelor - Mining Revue no. 1 / 2012

Fig. 3 Order of percentage for loading machines

Fig. 5 Order of percentage for repairing time needed for loading machines

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Fig. 6 Order of failure for subassembly

Fig. 8 Order of repairing time for subassembly

One observation is that the loading machines type Mp1B, Mp2B and Mp5A have the most often failures, getting to a number of over 52% from the totally failures and about 67% for repairing time.

The presented histograms shown that the rotating system is the most affected subassembly by failure, as a number of failures, 42,5% from totally, and as a number of time repairing, 44%, that’s why this item will be studied more careful.

After this, there is a number of failures to the displacement system; the main failure is on electrical engine, 22,5 % and belt conveyers from the loading arm, 20%. The repairing time is very long and has a very high percentage, 30,5%. For the displacement system, the percentage is 17%, because of the time needed for vulcanization.

3. The maintenance study of rotating system The maintenance study of rotating system has as a cornerstone the statistical series made by n=17 values which represent the time, in hours, of repairing the rotating system, after the accidental failure. The statistical series is made by the following values: 2; 2; 3; 3; 3; 4; 4; 4; 4; 4; 4; 4; 4;

Fig. 7 Order of percentage for failure for subassembly

Fig. 9 Order of percentage for repairing

6; 8; 8; 16, being a (S2) serial type, where a part of values are being repeated.

The probability distribution of this serial, which represent the empirical maintenance function which characterize the functionality of rotating system, results from the reckoning shown in table 3.

The literature shows that maintainability of electromechanical systems is best characterized, generally, by the laws of a negative exponential distribution, normal, lognormal or Weibull.

The choice of the distribution law is made on the basis of a test between empirical (experimental) distribution and the theoretical one, from which, the Kolmogorov-Smirnov and χ2 (square hi) are the most used. The specific maintenance parameters for distribution laws are determined by punctually estimation methods, from which, the most used are: maximum likelihood method, method of least squares, method of moments and linearization method.

By applying these specific reliable techniques of statistical series which characterize the rotation system's maintainability has come to the conclusion that the dual parametric distribution law of Weibull Revista Minelor - Mining Revue no. 1 / 2012

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is the best, for which parameters were calculated by the method of least squares; validating the model

with the Kolmogorov-Smirnov general test.

Table 3. The reckon of empirical maintenance function Relative Values of repairing time, Absolute abundance, The empirical maintenance function (order), abundance, No. ˆ (t ) tr , h ni M r fi 1 2 3 4 5 6

2 3 4 6 8 16

2 3 8 1 2 1

0,117647 0,176471 0,470588 0,058824 0,117647 0,058824

0,117647 0,294118 0,764706 0,823529 0,941176 1,000000

The values of Weibull’s dual parametric distribution parameters are calculated with: - the shape parameter, β, ⎡ n 1 n ⎢ ∑ ln ln 1 − Mˆ i =1 ⎣ β =

⎤ ⎡ n ⎤⎛ n ⎞ 1 ln t ri ⎥ − ⎢ ∑ ln ln ⎥ ⎜⎜ ∑ ln t ri ⎟⎟ ˆ (ti ) 1 − M ( t ri ) ⎦ ⎝ i = 1 ⎠ ⎦ ⎣i =1

⎡ n n ⎢ ∑ (ln t ri ⎣i =1

⎞ ⎛ n − ⎜⎜ ∑ ln t ri ⎟⎟ ⎠ ⎦ ⎝ i =1 ⎤

)2 ⎥

,

(1)

2

- the λ parameter, ⎧⎡ n ⎤⎡ n 1 2⎤ ⎪ ⎢ ∑ ln ln ⎥ ∑ ( ln t ri ) ⎥ − ˆ 1 − M (t ri ) ⎦ ⎢⎣ i = 1 ⎪ ⎣ i =1 ⎦ λ = exp ⎨ n ⎡ ⎤ ⎪ n ⎢ ∑ (ln t ri )2 ⎥ ⎪ i = 1 ⎣ ⎦ ⎩

⎤⎫ ⎛ n ⎞⎡ n 1 ⎜⎜ ∑ ln t ri ⎟⎟ ⎢ ∑ ln ln ln t i ⎥ ⎪ ˆ 1 − M (t i ) ⎝ i =1 ⎠ ⎣ i =1 ⎦⎪ ⎬ 2 n ⎛ ⎞ ⎪ − ⎜⎜ ∑ ln t ri ⎟⎟ ⎪ ⎝ i =1 ⎠ ⎭

. (2)

- the real scale parameter, η,

η =

1 .

1

(3)

λβ The results of this method application are shown in table 4.

Table 4. The calculation elements specific for rated Weibull dual parametric distribution parameter using the method of least squares and checking its accuracy 1 ln ln ⋅ 1 2 ˆ ln ln ln t ri M (t ri ) M (tri ) − Mˆ (tri ) M (t ri ) − Mˆ (t i −1 ) 1 − M (t ri ) i t ri , h (ln t ri ) ˆ 1 − M (t ri ) ⋅ ln t ri 1 2 0,693147 0,480453 -1,440455 -2,078137 0,256122 0,138475 0,256122 2 3 1,098612 1,206949 -1,158675 -1,054672 0,368145 0,074027 0,250498 3 4 1,386294 1,921812 0,512148 0,369436 0,465810 0,298896 0,171693 4 6 1,791759 3,210402 0,986861 0,550777 0,622008 0,201521 0,142698 5 8 2,079442 4,324077 2,165554 1,041412 0,735180 0,205996 0,088349 6 16 2,772589 7,687248 0,000000 0,000000 0,940137 0,059863 0,001039 6 6 6 6 1 1 ∑ ln t ri = ∑ (ln tri )2 = ∑ ln ln 1 − Mˆ (t ) ⋅ ∑ lnln Dmax= ˆ 0,256122 1 − M (t ri ) ri i =1 i =1 i =1 i =1 0,298896 ⋅ ln t ri = 1,065432 =-1,171184 =18,830941 =9,821844 2 ⎛6 ⎞ ⎜ ∑ln t ⎟ = ri ⎜ ⎟ ⎝i=1 ⎠ =96,468611

Dmax = 0,298896 < D0,05 , 17 = 0,317963 Kolmogorov-Smirnov test Shape parameter, β = 1,083474 Relaţia (1) λ parameter = 0,139622 Relaţia (2) Real scale parameter, η = 6,154187 h Relaţia (3) The main maintenance indicators expressed by Weibull’s dual parametric distribution law are shown in table 5.

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Table 5. Calculation formula of indicators expressed by rated Weibull’s dual parametric distribution law

Nr. crt.

Parameter

Symbol

Formula

M (t r )

⎛t − ⎜⎜ r η M (t r ) = 1 − e ⎝

Maintenance 1 function

4

β

, (4) ⎛t ⎞

Function of 2 probability density of repairing time 3

⎞ ⎟⎟ ⎠

f (t r )

Function of intensity or repairing rate

z (t r )

Average of repairing time

MTR

β −1 − ⎜⎜ r ⎟⎟ β ⎛ tr ⎞ η f (t r ) = ⎜⎜ ⎟⎟ e ⎝ ⎠ η ⎝η ⎠ (5) β −1 β ⎛ tr ⎞ z (t r ) = ⎜⎜ ⎟⎟ , (6) η ⎝η ⎠

Observation

M.U.

tr – fluctuation of repairing time, h; β – shape parameter; η – real scale parameter, h

%

β

1/h

,

1/h

Γ - Gamma function or Euler’s integral, type two,

⎛1 ⎞ MTR = η Γ⎜⎜ + 1⎟⎟ , (7) ⎝β ⎠

∞

Γ( p ) = ∫ x p −1 e − x dx ,

h

0

p >0,

TMMC

TMMC = η (− ln 0,5)1 / β , (8)

h

Tmax 90

Tmax 90 = η (− ln 0 ,1)1 / β , (9)

h

Tmax 95 Tmax 95 = η (− ln 0,05)1 / β , (10)

Mentenabilitate, %

In figures 10, 11 and 12 there are shown the main indicators which characterized the maintenance of rotating system of loading machines from Turceni power station coalyards.

1 0.9 0.8 0.7 0.6 M ( tr)0.5 0.4 0.3 0.2 0.1 0

Densitatea de probabilitate, 1/h

Median time of 5 corrective maintenance Maximum time of corrective 6 maintenance for a 90% probability Maximum time of corrective 7 maintenance for a 95% probability

h

0.15 0.12 0.09 f ( tr ) 0.06 0.03 0

0

5

10

15

20

25

tr 0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 tr

Timp de reparare, h

Timp de reparare, h Fig. 11 Time repairing probability density curve

Fig. 10 Maintenance function curve

Revista Minelor - Mining Revue no. 1 / 2012

Intensitatea de reparare,1/h

10 0.25 0.2 0.15 z ( tr ) 0.1 0.05 0

0

5

10

15

20

25

30

tr

Timp de reparare, h Fig. 12 Intensity curve or repairing rate

Average time for repair MTR = 6 hours, and median time of corrective maintenance TMMC = 4,4 hours. Maximum time of corrective maintenance, for a 90% probability is Tmax90 = 13 hours, and for 95% probability, Tmax95 = 17 hours.

From the figures shown above, the probability for rotation system of getting back to work in 4,4 hours is only 50%. For a 80% probability, the repairing time goes up to 10 hours, big values, considering the machinery’s construction.

It can also be seen a very low fluctuation of repairing intensity, (0,15...0,20) repair/hours, the values of this parameter is very low as well, but its relative constancy is explained by the uniformity of operating teams, in terms of promptness action, facility with tools and spare parts, with action machineries and not at last their experience.

The higher values of corrective maintenance time owe to the ineffectual management of maintaining activity. This statement is based on the argument that the adopted maintenance strategy for the rotation system, and for the whole machinery is for the corrective maintenance, based on repairing actions for unexpected failures, for getting back the product to its best quality. For this action, the main goal is to get off the unexpected failures.

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Obviously, such corrective maintenance actions have: - insurance of the specialized personnel, when the failure appear; - failure diagnosis, finding the nature and the cause of the failure; - locating the failure; - ensuring the spares, tools, consumables and other things for repair; - repairing the failure by complete or partially replacing of a part or many elements or subassembly which were the cause of failure; - checking the maintenance operations.

Each of these elements represent a substantial time of inefficiency.

There is one way to reduce the time used for repairing the failures, respectively the time for parking, by embracement a preventive-scheduled maintenance strategy, used for having checked the vulnerable elements and operate to the weak observed points, which mean to reconsider or embracement a new maintenance strategy.

4. Conclusions The study on the loading machine from coalyards show a long list of failures, mainly to the rotation system, which confirm the low reliability of this machinery and impose to reconsider the functional and design solutions.

The corrective maintenance system applied is totally impropriate, being necessary to embracement the preventive-scheduled system for maintenance and repair.

References 1. Fodor, D. The exploitation of mineral and useful rock deposits in open pits, Vol. 1, Editura Tehnică, Bucureşti, 1995.

2. Jula, D., Dumitrescu, I. The fiability of transport systems, Editura Focus, Petroşani, 2009.

3. * * * Technical documentation of the deposit loading machine type T 2052

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MODIFICATION OF THE STATE OF STRESSES AND STRAINS AROUND THE CAVITIES RESULTED AFTER THE EXPLOITATION OF SALT BY DISSOLUTION CASE STUDY: OCNELE MARI EXPLOITATION Monica ANDREI* Abstract Due to the complex geological aspects, the stability and management of the caverns produced in salt by dissolution represent a very difficult task. The special properties of the salt – low conductivity, viscous-elasto-plastic behavior – made salt suitable for hydrocarbons and high-active waste storage in caverns produced by dissolution, beside the actual salt exploitation. At the same time, beside the location investigation made by various methods, it is necessary to evaluate by calculus the stability of the cavern in various exploitation conditions. Among the methods used for this, the numerical modeling presents undisputed advantages because is using all the existing information and permits the cavern behavior simulation in relation with the existing loadings.

The numerical modeling of the stress and strain around the salt dissolution caverns is intended to simulate the controlled collapse progress of the main cavern in Filed I – Ocnele Mari.

Key words: cavern, numerical modeling, monitoring, safety factor 1. Introduction The exploitation of the Ocnele Mari deposit was performed by salt dissolution, a technology which involves the injection of sweet water flows that dissolve the salt by means of a well system. The outcoming brine is extracted by means of the same well system and it is delivered to the processing plants.

The exploitation of the salt deposit through solution mining results in the formation of caverns filled with brine under pressure. It is crucial to maintain the mechanical balance of the cavern during the exploitation of the system through brining. For this purpose, the exploitation technique involves the development of cylindrical caverns, centered around the well, maintaining a salt layer in the roof of the cavern, thick enough to ensure its balance.

To the extent possible, the exploitation shall be performed outside the populated areas in order to avoid any serious consequences, in case of a _____________________________ * Ph.D stud, eng. University of Bucureşti

potential collapse. At the same time, the system’s behaviour is continously monitored, supervising the evolution of subsidence through surface measurements and the evolution of the cavern through cavernometric measurements. Lately, the monitoring system is supplemented by monitoring the cavern’s induced seismicity, in order to highlight the stress concentration areas.

These requirements were not complied with in case of the exploitation of Ocnele Mari deposit, as the wells were dug at small distances one from another, thus determining an uncontrolled exploitation.

Given the fact that the salt deposit base contains sterile gangue material, eroded due to the exploitation process, the individual caverns of the wells merged together, resulting in the formation of cavities of signifiant volume. Hence, in the Well Field II of Ocnele Mari, the common cavity had a volume of approximately 4.3 milion m3. The accidents occurred during a period of 4 years, brought about unpleasant situations, having an impact both on the local community (many families had to relocate) and on the environment. Also, a cavern with a volume of nearly 1 milion m3 was present in the Well Field I, such cavern being defused in 2009.

The evaluation of the cavern stability actually involves the calculation of the state of stresses and strains in the geological complex where the cavern was opened. Due to the complex geometry, the variation of the geomechanical properties, as well as due to the constitutive rock behavior laws, the analysis of the state of stresses presents a very high level of difficulty. The only method able to take into consideration all elements in case of unsteady loads is the numerical modeling.

This work has two objectives: Analysis of the evolution of the state of stresses and strains during the defusing of the situation in the Well Field I of Ocnele Mari Correlation of the integrated monitoring system results with the distribution of the state of stresses and strains, obtained through numerical modeling 2. Geological conditions The Ocnele Mari salt deposit is located in the Lower Carpathians Hills of Oltenia, at a distance of about 10 km westwards from the municipality of Rm. Vâlcea.

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Masses from the Paleogene, Neogene and Cuaternary age are present in the area.

The Ocnele Mari salt deposit occupies the northern flank of the Govora – Ocnele Mari anticline (fig. 1),

being limited by the Copacelu fault in the East and the Teiuș fault in the West. Also, the salt deposit is limited by the Stoenești fault in the North and the Bisericii fault in the South (fig. 2).

Fig. 1 Geological layout of Govora - Ocnele Mari area

Fig. 2 Geological section of the Ocnele Mari deposit

The salt deposit is lens shaped, having a length of 8 km, a width of 3.5 km and a total surface of about 30 km2. The masses in the deposit’s roof belong to the Upper Badenian age and those in the floor belong to the Lower Badenian age. The NaCl content of the deposit is 98-99%. The thickness of the deposit varies from a few metres in the pinching-out area to 473 m. The average thickness of the deposit is of 250 – 300 m.

The exploitation of salt through solution mining at Ocnele Mari started in the 1960s and it was carried out in time by means of four well fields. Currently, the exploitation only continues in Fields III Lunca and IV, Fields I and II being decommissioned. Well Field I consisted of 10 wells (fig. 3). The exploitation of this field started in 1960 and went Revista Minelor - Mining Revue no. 1 / 2012

on until 1973. At the beginning of the exploitation, the wells were operating individually, but, due to the circulation of fluids through the interlayers of the salt deposit, the cavities of the wells merged together over the time.

In 2006, after the defusing of the situation in the Well Field II, having in view the influence of the phenomena occurred in this field over the Well Field I (the two fields were hydraulically communicating through the sterile interlayers within the salt deposit), the wells in Field I were cavernometrically measured. The performed measurements revealed the presence of a cavern of approximately 1 milion m3 in field I. Following the identification of this cavern, the systematic monitoring of this field was initialized.

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The monitoring involved cavernometric measurements, topographic measurements, level measurements, as well as microseismic monitoring.

During the 3 year period until the defusing of the situation, the salt ceiling above the common cavity of the wells in Field I, gradually crushed down.

Hence, while in January 2006, the surface having a salt layer with a thickness of less than 10 m was of about 3600 m2, in January 2009, the surface was of about 8000 m2 (fig. 3).

The continuous moving-up of the cavern’s ceiling is reflected in the evolution of the sinking, their gradient increasing from 1.1 cm/year in 1995 to 2.5 cm/year in 2007 and locally up to 9.1 cm/year - at the beginning of 2009.

These two elements – the moving-up of the ceiling and the continuously increased sinking, led to the conclusion of an imminent collapse of the cavern’s ceiling.

In order to avoid the consequences of this process, the Research Department of Geology and Ambiental Geophysics proposed a project for the defusing of the situation in the Well Field I. In 2007, when the ceiling segmentation process was speeding up, a measure of stabilization of the system was implemented, by introducing concentrated brine in the cavern and by maintaining a high level of the brine.

mp 5 80 474 0 794 4

S uprafete cu grosi m i i ntre 5 s i 1 0 m

S uprafete cu grosi m i i ntre 0 s i 5 m

mp

mp 0

S uprafete fara tav an de sa re

250

1 852

212 4

3 650

553 0

Fig. 3 Evolution of the salt platform thickness in the ceiling of the common cavity from Field I –2006-2009

The Research Department of Geology and Ambiental Geophysiscs– of which I am a member, operating within the Faculty of Geology and Geophysics of the University of Bucharest proposed a project for defusing the situation in the Well Field I. After the approval of the abovementioned project, the proposed works were initialized. Principle of the project: gradual reduction of the piezometric level in the cavern and the takeover of the brine volumes by the chemical plant. Firstly, a dam was built on Pârâul Sărat creek, which was intended for the takeover of the brine volumes pushed out from the cavern; connections were established between the wells and this dam; 3 pumps were installed in wells 361, 368 (wells belonging to Well Field II, situated in the South of Field I and 370 from Field II, situated in the North of Field I – the three wells establishing a hydraulic connection with the cavern consisting of the wells in Well Filed I); a buffer tank was installed on the route of the connection pipes

between the wells where the pumps were installed and the brine duct.

In July 2009, it was decided to initiate the controlled collapse of the cavern in Well Field I. For starters, on July 14th, the level was let free (no brine was introduced in the cavern), and later, on July 28th the reduction of the level through the three pumps was initiated.

Fig. 4 Distribution of the sinking

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During the period July 15th – August 7th, several land cracks were revealed (photo 1-2), suggesting a potential rupture area and the sinking recorded a maximum level of 42 cm (in the area of landmark S1) during this monitored period (fig. 4).

Photo 1-2 Land cracks

Photo 3 Crater – August 8th, 2009

On August 8, a land crease funnel was revealed in the area of well 358, situated in the South of the cavern. The crater extended until the evening of that day (photo 3).

Following the topographic surveys performed on August 11th, the surface of the crater lake was determined to be of about 1800 m2 and the surface of the crater of 6900 m2, while on September 3rd, upon the performance of additional topographic surveys, the surface of the crater lake was determined to be of about 9700 m2 and the surface of the crater of about 25000 m2 (fig. 5).

During the brine spill process, both gravitationally and by pumping it towards the barrier on the Pârâul Sărat creek, the flanks began to get stabilized and the level of the crater lake began to decrease.

The crater lake currently exists only due to rainfalls (photo 4). The natural sloping continues, however, the evolution rate is insignificant and is not very easily detected, at a visual inspection.

Practically, the cavern in the Well Field I was decommissioned and, at the same time, the common cavity of wells 357 and 359 (belonging to Well Field I) was filled with sterile.

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Fig. 5 Evolution of the lake – September 3rd, 2009

Due to the complex geological conditions, the stability and the management of the caverns created in salt deposits through dissolution represent a very difficult problem. The special properties of salt – low conductivity, the viscous, elastic and plastic behaviour, apart from the actual exploitation of salt, led to the creation of caverns by dissolution, for the storage of hydrocarbons or highly-active waste. At the same time, apart from the inspection of the site, performed by various methods, it is necessary to Revista Minelor - Mining Revue no. 1 / 2012

perform an evaluation by calculation of the stability of the cavern in different exploitation conditions.

Among the familiar calculation methods, the numerical simulation presents undisputable advantages, as it incorporates all the existing information and it allows the simulation of the cavern’s behavior according to the requirements.

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July 15th, 2009, when the level of the brine was maximum, namely 285 m. This is the start moment of the controlled collapse process, characterized by discontinuation of the artificial supply; • July 28th, 2009, when the level of the brine was of 278 m. This moment corresponds to the lowest level registered by the brine in free spill; • August 7th, 2009, when the level of the brine was of 252 m, the moment prior to the collapse occurred on August 8th and during which the last settlement measurements were performed.

For each of the abovementioned moments, the following calculations are performed for each of the four sections: distribution of the displacements, of the main and shearing strains, the distribution of the main effective stresses, of the deviator and of the relative shearing stress. The evolution of the stability factor is also calculated.

The geomechanical parameters introduced in the model were taken from the determinations made available by SEM Vâlcea. The average values thereof were taken into consideration for the samples analyzed in the area of Ocnita (in the area of Well Field I), the designing of the model being performed according to the correlations between the absolute land displacements measured during the period June 14th – August 8th, 2009 and the absolute displacements calculated through modeling by the finite elements method, during the same period.

The geomechanical parameters resulted after the designing of the model: for salt E = 1.075*107 kN/m2, μ=0.3, c = 2000 kN/m2, φ = 40o, σt = 1000 kN/m2, γu = γs = 22 kN/m3, for sterile E = 7.5*105 kN/m2, μ=0.25 , c = 250 kN/m2, φ = 25o, σt = 100 kN/m2, γu = 19 kN/m3, γs = 21 kN/m3.

The performed analyses were used to determine the instability of sections 1 and 4, for which reason I am going to highlight the results obtained after the numerical modeling performed for these two sections (fig. 6 and 7).

•

Photo 4 Chimney collapse – June 2010

3. Numerical modeling of Well Field I evolution The numerical modeling of the state of stresses and strains around the caverns resulted due to the dissolution of salt through solution mining, aims at simulating the evolution of the controlled collapse of the cavern in Well Field I – Ocnele Mari. The simulations were performed through PLAXIS 7 program, which calculates the distribution of the state of strains and stresses in the rock masses, using the finite elements method in elasto – plastic behaviour.

The simulations was made by Finite Element Method, in plane-strain conditions. This approach is frequently used in engineering practice, because it involves an infinite development of the caverns on the perpendicular direction, the results being secured. The domain was developed with an equivalent value of the cavern extension, on the both lateral sides (left and right) and also in the bottom of the section.

The particularities of this program are the following: the use of certain 15 nodes triangular finite elements and a wide range of constitutive laws, as well as a system for easy data entry and information processing.

The advantage of this method is that it enables the determination of the general stability factor of a section, as well as of the stability factor of each point in the section (determined as the reverse of the relative shearing stress).

The program calculates the stability factor by the phi-c reduction method. This method entails the successive increase of the stability factor, the recalculation of the resistance parameters and the recalculation of the maximum stresses and strains up to the moment when the resistance parameters begin to decrease, thus leading to the failure of the structure. The rupture is indicated by the nonconvergeance of the solution, after a large number of steps.

Four sections, intersecting with the common cavern in Field I, were selected for the simulation of the controlled collapse process. An analysis of the distribution of the state of stresses and strains is performed for each section, in three different stages of the collapse process:

Fig. 6 Section 1 Revista Minelor - Mining Revue no. 1 / 2012

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Fig. 7 Section 4

Fig. 8 Section 1 –displacements calculated on August 7th, 2009

Fig. 10 Section 4 – deviator June 14th, 2009

•

•

the deviator is concentrated in the area of the inter-chamber pillars and in the cavern’s arches, up to the sterile-salt contact; the shape of the distribution is maintained for all level values, however, its value increases simultaneously with the decreasing of the level (fig. 10 and 11); if, unsurprisingly, the main efforts have maximum values in the area of the interchamber pillars, in sterile, above the main cavern (fig. 12), the maximum main stress is a tensile force suggesting the segmentation of the material, after surpassing the tensile strength.

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After analyzing the results, the following conclusions are drawn: • among the analyzed sections, sections 1 and 4, particularly section 4, present the largest settlements, approximately 1.27 m, when the level of the brine is of 252 m (fig. 8 and 9).

These sections intercept the apex of the cavern, in the area where it is in direct contact with the sterile; • the distribution of the displacemnets is concentrated in the area of the future chimney, the curves of equal displacement having the shape of balance arches; this distribution represents an additional confirmation of the conceptual model used within the controlled collapse project (fig. 8 and 9).

Fig. 9 Section 4 – displacements calculated on August 7th, 2009

Fig. 11 Section 4 – deviator August 7th, 2009

Fig. 12 Section 4 – total main stresses – August 7th, 2009

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For sections 1 and 4, the stability factor decreases down to values adjacent to the unit F=1.075, for section 1, namely F=0.964, for section 4, when the brine reaches a level of 252m, indicating the cavern’s roof collapse. This represents in fact, the altitude at which the main cavern’s roof collapse in Well Field I began.

displacements, determined after the topographic surveys performed on the field, a maximum value of 41 cm being determined for section 4.

Fig. 15 Variation of settlements at the level of the land surface for the 4 sections

Fig. 13 Variation of the stability factor for the 4 analyzed sections

From the point of view of the determined vertical displacements, the maximum levels registered for the four sections were present at the level of the cavity’s ceiling, which were slightly decreasing towards the surface. Hence, the maximum displacements registered at the level of the cavity’s ceiling were revealed for sections 1 and 4, at a level altitude of 252 m, having values of 0.47 – 0.52 m, turned into absolute values – starting July 14th – at a level altitude of 285 m (fig. 14).

The correlation of the integrated monitoring results with the modification of the state of stresses and strains, aimed at creating a coherent image of the geomechanical behaviour of the Well Field I, according to the measurements and the numerical simulation. Four types of measurements were analyzed within the monitoring system assembly: cavernometry, level, evolution of settlements and induced seismicity.

Due to their accuracy, the cavernometric measurements are essential for the characterization of the system geometry evolution. Hence, the cavernometric measurements performed by using the SOCON German company’s equipment and technology, enabled the outline of the common cavern, as well as its connection with the caverns and the cavities of the nereby wells. Following the periodic performance of the cavernometric measurements, a decrease in the thickness of the salt layer was revealed in the main cavity’s ceiling and, since September 2006, of an area where the salt on the ceiling completely disappears, the cavern being in direct contact with the sterile. The total volumes of the masses fallen down from the ceiling were also evaluated, from 10000 m3 at the end of 2006, to 90000 m3 in January 2009 (fig. 16 and 17).

Fig. 14 Variation of settlements at the level of the cavity’s ceiling for the 4 sections

After extracting the tables with the distribution of the vertical displacements, calculated in the nodes of the elements and upon the representation of these displacements for the geologic sections, the displacements calculated at the surface of the land, for the four sections, at the three different analyzed moments, were thus identified.

The maximum values, thus determined, are correlated with the maximum values of the

Fig. 16 Evolution in time of the volumes detached from the salt ceiling Revista Minelor - Mining Revue no. 1 / 2012

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LUNI

Fig. 17 Evolution in time of the salt ceiling surfaces with thicknesses below 5 m, 10 m, 15 m and 20 m

For example, during the period July – October 2007, the occurrence of a series of events towards the end of August (fig. 18) was ascertained, such events occuring at the level of the salt on the cavity’s ceiling. After the occurrence of this series of events, the cavernometric measurements determined the detachment from the salt ceiling of a mass with a volume of 25000 m3 (the inflexion point in fig. 16 and 17, correlated with the time interval corresponding to the occurrence of the microseismic events in fig. 18).

Fig. 18 Frequency of microseismic events in Well Field I - 10.07.2005 – 15.07.2009

The relations between the parameters measured or determined by calculation were presented from the perspective of the cavern’s evolution in Well Field I, however, taking into consideration the influence of the SOCON cavern defusing, such cavern belonging to Well Field II and being defused in 2005. The influence of the SOCON cavern defusing may be observed at the level of the settlements recorded in Field I, immediately after its collapse.

The relative correlations between the microseismic events and the other parameters resulted after the monitoring, were performed for time intervals corresponding to certain evolution peaks, quantified by massive material falls from the cavern’s ceiling in Well Field I, or for cavernometric measurements intervals performed for the determination of the cavity’s geometry in Well Field I. At time intervals common to measurements, the occurred microseismic events (Figures 19 and 20) were projected on the four geological sections (at a distance smaller than 10 m). The occurrence of the microseismic events, preeminently concentrated in Revista Minelor - Mining Revue no. 1 / 2012

the area of the inter-chamber pillars and in the area of the ceiling cavity pillar, corresponds to the distribution of the state of stresses and strains, determined through numerical modeling with finite elements.

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Fig. 19 Projection of microseismic events for section 1 (April-July 2008)

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The microseismic activity is related both to the cavernometric measurements and the redistribution of stresses pursuant to the evolution of the caverns’ geometry. Thus, by correlating the volumes detached from the cavern’s ceiling with the frequency of the occurrence of the microseismic events, it was pointed out that the detachments from the ceiling are always preceded by an increase in the frequency of the events (fig. 21). The induced seismicity, in this case, represents a precursor of the cavern’s evolution.

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Fig. 20 Projection of microseismic events for section 4 (April-July 2008)

Fig. 21 Correlation of the volumes detached from the salt ceiling with the frequency of the microseismic events

After analyzing the distribution of the microseismic events in the sections where the distribution of stresses was calculated, their grouping was presented, during the period April – July 2008, in the inter-chamber pillars and in the cavern’s salt ceiling. This concentrations lap over the areas of maximum distribution of the deviator, which leads to the conclusion that the source of the microseismic events is determined by shearing dislocations (Figure 22). On the contrary, in the period August 2008 - July 2009, the events are mainly concentrated in sterile: due to the loosening of the inter-chamber pillars, the loads are taken over by the competent sterile layers, which were thus fragmented.

Fig. 22 Section 4 – Correlation of the microseismic events (2008) with the distribution of the relative shearing stress

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4. Conclusions Pursuant to the analysis performed for the geotechnical evolution of the cavern in Well Field 1 and for the cavities of the nearby wells, the following conclusions are drawn up: - a cavern with a volume of approximately 1 million m3 resulted after the merger of six wells in Well Field 1; - gradually, the salt ceiling of the common cavity’s roof crushed down and, in 2009, it completely disappeared on a significant surface, thus leading to a short term limit balance; - The correlation of the integrated monitoring results, in the period 2006 – 2009 (topographic, level, cavern metric, micro seismic measurements) suggests the instability of the cavern in the Well Field 1, as well the implications generated by a sudden collapse, which would have involved serious consequences, firstly for the local population and then for a significant brine pollution of the environment, of Pârâul Sărat creek in particular, which flows into the Olt river.

- the results of the micro seismic monitoring, apart from the fact that they were able to be considered within the performed correlation, proved to be a real aid in anticipating the modification of the state of stresses and strains around the common cavern and the nearby cavities.

- the numerical modeling with finite elements enabled the determination of the stability factors for the analyzed sections, highlighting the future rupture area, also pointing out the rupture model taken into consideration for the elaboration of the cavern’s controlled collapse project.

- the correlations performed between the measured land displacements (topographical surveys) and those calculated through modeling

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with finite elements, enabled the creation of a viable model, which can also be used in other areas of salt exploitation through dissolution, such areas being geomechanically unstable.

The phenomena registered at Ocnele Mari mark the beginning of a period during which we shall face similar situations in other salt exploitation mining areas, as well. The ongoing phenomena, registered at Ocna Mureș, confirm the abovementioned statement. Consequently, we are entitled to consider this inherent analysis as a role model for similar situations.

References 1. Likar, J., Cadez, J. Three-Dimensional Numerical Analysis of Stress Strain Changes in Mine Structure in Velenje Coal Mine, Numerical Modeling in Geomechanics -- 2006 (4th International Symposium, Madrid, May 2006). Paper No. 02-09, R. Hart and P. Varona, Eds. Minneapolis, Minnesota: Itasca Consulting Group, Inc. 2. Young, R.P, Hazzard, J.F., Pettitt, W.S. Seismic and micromechanical studies of rock fracture, Geophysical Research Letters, Volume: 27 Issue: 12 3. Zamfirescu, F., Mocuţa, M., Dima, R., Constantinescu, T., Danchiv, A., Andrei, M. Technical solution and monitoring results of the controlled collapse of Field I salt cavern, Ocnele Mari, Romania, Solution Mining Research Institute Fall 2009 Technical Conference, Leipzig, Germany, 3-6 October 2010 4. Hoek, E., Diederichs, M.S. Empirical estimation of rock mass modulus. Int.J. Rock Mech. and Min Sci 200643,203-215.

5. Hoek, E., Carranza-Torres, C., Corkum, B. Hoek-Brown failure criterion - 2002 edition, Proc. of North American Rock Mechanics Symposium. Toronto 2002.

6. Jeremic, M.L. Rock mechanics in salt mining, Balkema, Rotterdam.

1994

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ORGANIGRAM OF UPGRADING AND OPTIMIZATION POWER STATIONS AT HIGH VOLTAGE, VERY HIGH VOLTAGE AND ULTRA HIGH VOLTAGE Nicolae Daniel FÎŢĂ*, Dragoş PĂSCULESCU**, Lucian FÎŢĂ***, Lucian DIODIU**** Abstract Upgrade the power stations at high voltage, very high voltage and ultra high voltage and transmission and distribution networks of electricity, is a key point in optimization european power systems UCTE, NORDEL, TSOI and UKTSOA. By upgrading and optimization improve reliability european systems, increased quality electrical energy, increased transit of electricity, reducing power consumption and eliminate accidents of works and occupational diseases.

The author of this scientific paper, in the context of upgrading and optimization of power stations 110, 220, 400, and 1000 kV designed organigram upgrading and optimization.

This organigram can be example for future upgrading and optimization of power stations all over the world.

Cuvinte cheie: organigram, optimization, power stations

diagram and restriction of land) and configuration (type high, average height, low height, mixt).

Power stations of inside type depend on prefabricated switchgears (line, transformers, coupling, measuring, compensation, surge arrester, etc.) and isolating gas (sulphur heaxafluoride SF6, compressed air and insulating oil, etc.)

upgrading,

1. Power stations – element of power systems A. Definition and role Power stations is the set of installations and annexes building in which the least one of the followings operations: electrical connections of two or more power sources (generators or centrals), the electrical connection of two or more ways to make a power transit, distribution electricity for consumers at the same voltage or other voltage (through power transformers or power autotransformers).

Fig. 1 Constructive aspects of power stations

C. Different schemes used for power stations SCHEME WITH ONE SYSTEM OF BUSBAR WITH 2 CIRCUIT BREAKER/CIRCUIT

B. Constructive aspects of power stations The upgrade of power stations depends on the type of station (outside and inside). Power stations of outside type depend on influences (single line 1234

* Ph.D. eng. Romanian Association for Electrical Safety ** lect. Ph.D. eng. – University of Petroşani *** Eng. SC CONTEAM SRL Bucureşti **** Ph.D.eng. - SC ENEL ENERGIE SA

W1, W2 – busbars; Q1 - Q4,– circuit breakers; S1 - S4 – disconnectors.

Voltage: 1000 kV, 750 kV, 400 kV, 220 kV, 110 kV.

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SCHEME WITH ONE SYSTEM OF BUSBAR WITH 1,5 CIRCUIT BREAKER/CIRCUIT

SCHEME WITH TYPE H SUPERIOR SYSTEM WITHOUT BUSBAR

Q1 – Q3,– circuit breakers; S1 – S4 – disconnectors; T1, T2 – transformer; LEA1, LEA2 – overheadlines.

Voltage: 1000 kV, 750 kV, 400 kV, 220 kV.

SCHEME WITH TYPE H INFERIOR SYSTEM WITHOUT BUSBAR W1, W2 – busbars; Q1 – Q6,– circuit breakers; S1 – S16 – disconnectors; T – transformer; LEA – overheadline.

Voltage: 1000 kV, 750 kV, 400 kV, 220 kV.

SCHEME WITH POLIGONAL SYSTEM WITHOUT BUSBAR

Q1 – Q3,– circuit breakers; S1 – S9 – disconnectors; T1, T2 – transformer; LEA1, LEA2 – overheadlines.

Voltage: 1000 kV, 750 kV, 400 kV, 220 kV.

2. Criteria for choice of apparatus and electrical equipments a) nominal electrical characteristics : - rated voltage use Ue, rated insulatation voltage Ui, rated impulse voltage Uimp; - rated current use Ie, rated current uninterrupted Iu; - nominal frequency.

Q1 – Q4,– circuit breakers; S1 – S12 – disconnectors; T1, T2 – transformer; LEA1, LEA2 – overheadlines.

Voltage: 1000 kV, 750 kV, 400 kV, 220 kV.

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b) behavior under shortcircuit: - short-term permissible rated current Icw; - nominal capacity of shortcircuit shutdown Icm; - nominal capacity of shortcircuit breaking Icn; - the rated shortcircuit condition.

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Fig. 2 Criteria for choice of apparatus and electrical equipments

3. Organigram of upgrading and optimization power stations

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4. Concluzii In organigram upgrading and optimization power stations is presents methodology of upgrading, step by step, each step is well definited and structured.

Applicability to power station for following voltage: 1000 kV, 750 kV, 400 kV, 220 kV, 110 kV.

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References 1. Fîţă, D. Aspects of upgrading and optimization power stations – Ph.D thesys, Universitatea Technical University of Cluj Napoca, 2011; 2. Fîţă, D., Moraru, R., Breben, F., Iorga, N., Păsculescu, D., Păsculescu, V., Mihai, N. Electrical safety in work, Editura Universitas, Petroşani, 2011.

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ANTHROPOGENIC ACTIVITIES FROM THE MOTRU MINING BASIN TRIGGERING EMERGENCIES Ioan-Liviu PIPIRIGĂ* Abstract: The anthropogenic activities and especially the mining ones from the Motru mining basin cause drastic modifications in the morphology of the region, in the continuity and the evolution of the vegetal soil, in the unfolding of the flora and fauna assemblies, in the economy and agricultural and forestry use of the lands, with significant effects on the local microclimate.

The mining activity generates uncertainties or even the reduction of the urbanisation and modernisation rhythm of the localities and the individual households, because of the lack of future development of the extractive activities.

The influences related to the energy coal revaluation on the territory of Motru Municipality has had important implications on the fund, on the ecosystems regarding agriculture and forestry, as well as the ones regarding the hydrology, the communication ways, the ones related to the human settlements, as well as the ones related to the flora and fauna of the minable perimeters.

1. Introduction The problems related to the protection of the environment have occurred in the last decades, when the disturbance of the natural balance between the components of the biosphere was discovered, as a consequence of the strong development of the industrial processes and the absence of the measures to maintain that balance.

The development of the anthropogenic activities has numerous direct and indirect implications on the environment and it is a source of its status change through various impact forms.

The issue of the emergency situations has become one of the most common ones at world level due to the climatic changes and the disasters with humanitarian consequences, to the actions or inactions of some members of the society that have as a result the occurrence of effects that are especially harmful to the social and natural environment.

The category of emergency situations may include the impacts on the environment due to the _____________________________ * Ph.D eng. University of Petroşani

emissions, discharges or evacuations into the air, on the ground or in the waters of the wastes, the liquids or the harmful energies (radiations, vibrations, noises, excessive heat) or due to the poor management of these wastes or energies released, following technological faults, fires, explosions, etc.[4].

The events generating the emergency situations, in their majority, can be prevented, and the ones that cannot (such as the earthquakes) can be managed, their effects could be reduced through a systematic process involving the setting of measures and actions meant to contribute to the reduction of the risk associated to these phenomena.

A feature of the emergency situations management is the fact that the predictability of the place or of the area of occurrence of the respective situations determines the possibility of warning the local authorities, the economic operators and the persons that may be in the areas that may be affected.

2. The description of the Motru mining basin The Motru mining basing (fig.1) appeared in the toponimy and the geographic reality in the year 1960 when the first coal mine was opened (Horăşti mine). The name of this exploitation perimeter was taken from the natural frame, from the hydrography of the area. The very wide valley of Motru that set very good conditions for small urban localities is also the one that has lent its name to the entire basin. The main element for the identification of this basin besides the relief, which it overlaps, is the hydrography[1].

The Motru mining basin is located on the middle course of Motru river and its tributaries.

The connection between hydrography and coal is a favourable one. First of all, because the rivers, through erosion, have discovered the rich layers of coal that crop out their banks, as it happens in Meris on Motru Valley, in Ploştina on Valea Cireşului. First, because the valleys have offered communication ways that are favourable to the extraction of the rich coal deposits.

The majority of the mines, from the surface as well as underground are located along the courses of different rivers: Lupoaia on Lupoiţei Valley, Ploştina on Cireşului Valley, Roşiuţa on Potângul Mare and Potângul Mic Valleys, Horăşti on Fântâna lui Cuţui Valley, Leurda on Leurzii Valley, Boca on Matca Boca Valley[5].

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Fig.1 Motru mining basin

3. Anthropogenic activities in the Motru mining basin and their impact on the environment The anthropogenic activities have an impact on the environment as a result of the transformations in the use of the territory, of the construction of productive installations and infrastructures, of the emissions of chemical compounds in the atmosphere, of the discharges of waste waters in the natural receivers, of the use of chemical substances in agriculture or of other dangerous substances, etc.

The mining industry is the main source of pollution of the environment in the Motru mining basin. Among its negative effects on the environment and on the health, we have to mention the pollution of waters, with a high content of residues, mainly inorganic, the pressures on the quality of the soil resulted from the mining activity, the landslides (such as the ones from Bujorăscu Valley and Ştiucani Valley), etc.

The current mining exploitations from the Motru mining basin have a varied and complex influence on the environment as follows: • the temporary or permanent coverage of some surfaces of land affecting, in some cases, the hydrogeology and the neighbouring relief; The achievement of the industrial mining objectives from the mining basins of Oltenia implied the removal from the agricultural and forestry circuit of large surfaces of land. In the period 1952-2001 over 17,000 ha of land were removed from the circuit, of which 76% agricultural lands and 24% forestry lands. Of the agricultural ones, 61% were arable, 23% natural meadows, 9% grasslands, and the rest was unproductive. The orchards represented 7% and the vineyards 1%.

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Related to the current brown coal mines, the extraction and the dewatering activities lead to the reduction of the phreatic layer, not only in their perimeters but also on large surfaces, affecting the water supply of the economic units and the neighbouring localities.

At the same time with the movement of the working sites in the quarries, the fields from the meadows and the forested hills from the hill area disappear, and the initial heaps of debris represent a degradation of the landscape.

• the degradation of the soil, the pollution of the air and of the waters; The current mines affect the fertile soil and the normal continuous development of the flora from the area at the same time[3].

The removal of the vegetal soil from the surfaces of the future quarries, even if it is performed with great care, leads to its degradation from a physical and chemical point of view. In addition, the presence of the heaps of debris along some valleys, but also in former meadows, under the form of irregular geometry deposits, gives these areas a moon-like landscape appearance. In general, the current mining activities lead to the profound change of the relief in the respective area.

The quarries and the heaps of debris during the extended drought and wind produce the pollution of the atmosphere. The environment may be influence by the heaps of debris and the deposits that burn.

The waters from the quarries may have different quality and by discharging them may lead to the degradation of the quality of the water as well as the destruction of the flora and the fauna. the partial or total degradation of the soils and of the landscape.

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•

the change of the hydrographical conditions; Both the current mining activities and the constructions and installations from the surface often impose important hydrographical changes in the area through the deviation of courses of rivers or the execution of special hydrotechnical works.

Thus, in the mining basins of Oltenia, the courses of rivers like Jiu, Tismana, Jilţ and Motru had to be deviated, on lengths ranging between 5 and 40 km as well as the building of retention and reduction dams, such as the one from Rovinari.

• the change of the social conditions of the people from the areas affected by the mining activities; These changes consist of the movement of localities, the destruction of old localities with which the inhabitants have been connected for generations, even if the living conditions do not correspond to the new social changes in the majority of the cases.

Giving up the native places is very difficult.

Villages like Rovinari, Bălăceşti, Ceauru, Bohorelu were moved in their entirety, others only partially. Over 2000 households were moved in a period of over 50 years and other shall be moved in the future, such as: Roşia de Jiu, Timişeni, Găleşoaia and others. New localities have appeared: Băleştinew village, Drăguţeşti-new village, Ceauru, the towns of Motru, Rovinari and Berbeşti.

• the sound pollution The noise produced by the operation of machines from the current mining activities frequently disturbs the environment, especially the conveyor belts located near the human settlements.

The energy industry related to the Motru mining basin is responsible for the emissions of gases with a major impact on the environment. Thus, these activities produce 50% of the methane and carbon monoxide emissions, 97% of the carbon dioxide emissions, 88% of the nitric oxide.

An energy system is formed of a series of different activities, which deal with the production, the transportation and the distribution of the electric energy, each of these activities generating negative impacts on the environment.

The accelerated growth of the energy demand has been a feature of the human evolution ever since the industrial revolution, and, for several generations, this demand has been covered without taking into account the environment issues. Because of this, over time numerous accidents have been recorded being generated by the energy sector, which resulted in permanent ecological losses.

The emissions resulted from the energy sector contribute to the climatic changes, to the increase of the greenhouse effect, to the degradation of the ecosystems and have a major impact on the human health.

The identification of the maximum value of the quantities of assimilated pollutants in the environment and the definition of the sustainable development are necessary: the environment limits are the basic elements for the relative choice of production and the consumption of energy.

As we have shown above, the energy sector, together with the providing and consuming industries, is responsible for almost the entire quantity of carbon dioxide released in the atmosphere. The carbon dioxide emissions intensify the greenhouse effect and the consequences of this fact on the climatic changes of the planet. In 2003, the carbon dioxide emissions at a world level, coming from the burning of fossil fuels and wastes, reached a total value of 24983 million tons.

Agriculture contributes to the pollution of the natural environment through the use of a large volume of chemical fertilisers and pesticides, which reach, because of the surface flow, the lakes and the rivers and lead to the degradation of the fauna and the flora. The irrational exploitation of the lands has effects such as the degradation of the soil and the loss of surfaces from the agricultural circuit.

Transportation represents a major source of pollution by the placement of the communication ways and the release of the exhaust gases in the atmosphere.

4. Emergency situations generated in the Motru mining basin Subsidence phenomena Part of the brown coal deposits from the Motru mining basin was extracted through underground mining, applying various work methods and technologies.

The subsidence phenomena may be caused through the closing of the gaps remained after the underground extraction of the useful mineral substances and through the alteration of the hydrogeological conditions, due to the forced and high intensity dewatering of the aquifer system of the area[2].

When the underground excavations and especially the stopes exceed the critical dimensions from the point of view of the stability of the surrounding rocks and no support and closing the gasps measures have been taken, the covering rocks collapse triggering a complex of phenomena, known under the name of subsidence effects, which may extend along the thickness of the covering rocks, up to the surface.

The dimension of the surface degradation and the nature of the rock movement are influenced mainly by the following factors: the size of the gap created through extraction, the depth of the extraction, the thickness and the pitching of the deposit, the extraction method and technique Revista Minelor - Mining Revue no. 1 / 2012

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applied, the manner of directing the rock pressure, the geomechanical features of the rocks, the tectonic of the deposit, the duration of the extraction, etc.

We have to make the distinction between the dynamic effects that are produced during the extraction and the effects that last for a long time after the ending of the extraction, meaning that the new conditions of balance of the covering rock formations have been reached.

In the first case, the alteration of the surface structures (roads, railways, bridges, industrial and civil buildings, etc.) is caused by the both horizontal and vertical large deformations of the terrain surface.

The structures are subjected to the traction and compression efforts that may lead to destructions, as the case may be.

In the Motru basin, the vertical deformations, determined by the underground extraction of the brown coal deposits, varies between 100 and 3500 mm. In some cases, spectacular depths have been recorded whose value varies between 5000 and 6000 mm.

The brown coal extraction activity partially or totally affects the surfaces and the existing buildings from the perimeter under extraction and the ones from the perimeter needed to locate the heaps of debris and the infrastructure works.

These works have imposed the total or partial alteration of the villages from the location of the future mining or industrial buildings. It is estimated that a total number of 57 other localities shall be affected until the exhaustion of the mining resources.

Floods The floods are very dangerous because of the effects they produce. Thus, the devastating floods on Motru river happen every 15-20 years.

Moreover, the floods where the river water covered the entire major riverbed took place in 1979 and 1998.

Hydrotechnical works were executed in order to prevent the floods. Thus, deviation and river and stream regulation works were executed on a length of 76 km, protecting in this manner over 7680 ha from floods.

The Valea Mare dam is located on the upstream course of Motru, where its waters are deviated towards the accumulation from CernaSat, with a hydroenergetic and flow regulation role. In the middle section, the course of the river was regulated between Glogova and Valea Mânăstirii and dams were built near the heaps of debris from Valea Mânăstirii.

After the floods from 1979, the protection dam delimiting a part of the Motru major riverbed Revista Minelor - Mining Revue no. 1 / 2012

between Lupoiţei Valley and Ploştinei Valley near the town of Motru was resized in order to prevent such situations. The dam was built from battered ground, between 1964 and 1965, and it is covered with concrete plates towards the river, but the protection proved to be relative in 1998. Its role loss is due to the erosion and the lack of consolidation works, the water finding its way towards the urban space[5].

Landslides These have a high frequency within the entire Motru mining basin because of the geologic predisposition created by the presence of clays and marls alternating with the sands and the gravel.

The old landslides, currently stabilised, have been identified by the specific appearance of the level curves and emphasised on the land through the wavy aspect of the relief. They occur along rivers and have formed under the damaged stability of the slope because of the deepening of the valleys. Currently, they look like sliding waves, from place to place, these have been fragmented by erosion in small hammocks, such as the ones from Roşiuţa, beyond Bujorăscu at Vârtopu, on Gârdoaiei Valley, at Ciovârnăşani, etc.[6].

The active landslides have a typical evolution, such as the ones from Upper Peşteana Valley, at Ciovârnăşani and from Lupoiţei Valley.

Currently, based on the mentioned predisposition, we are witnesses to a new relapse of the landslides because of the mining activities.

The underground mining activities, through the gallery collapse (collapse lines have appeared), have led to the reactivation of some old landslides (e.g. Roşiuţa, Râpa, Lupoaia) or to the occurrence of new ones. Their feature is the disposition in narrow steps, creating over time a wavy relief such as the one at the north-west of Ştiucani village.

The quarries and the micro-quarries have produced very many landslides. These are minor landslides that occur on the slope, e.g. the landslide that affected the commune road PloştinaMiculeşti caused by the micro-quarry from Ploştina in the north as well as large landslides, characterised by the movement of entire slopes because of the stability disturbance. Although these have a potentially high danger, luckily the movement is very slow, found in a relative balance.

The heaps of debris have generated the largest number of massive and dangerous landslides.

The Ştiucani Valley heap of debris of the quarry from Roşiuţa, started up in 1988, is located in the upper area of Ştiucani Valley. Generally, the area is affected by landslides, but at the start of the

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deposits is partially stabilised. Between 1983 and 1988, the Ştiucani Valley heap of debris was used by the quarry from Jilţ Sud, which filled almost 70% from the upper area of Ştiucani Valley.

During this period, the depositing was achieved without taking into account the specific technology, with ascending deposits. However, the easier descending deposit technology was used, but with serious geotechnical flaws, confirmed by the numerous instability phenomena. It is considered that the landslides and compaction phenomena of the rocks from the cover of the stopes have reactivated several stabilised landslides, contributing to the occurrence of other massive landslides. These instability phenomena have been the result of the combination between the landslides and the compaction phenomena with the depositing system. The descending depositing was used until 1991, when numerous landslides occurred, so that the heap of debris could not be controlled any more. Since 1992 the ascending depositing has been started by lowering the heap of debris installation, so that around 2000 the heap of debris became relatively stable[8].

Between January and March 2006, landslides occurred that threatened ND67 on the Bujorăscu hill, as well as several human settlements from Roşiuţa locality. In May 2006, the heap of debris from Rogoaze Valley started to slide because of the deposits of the quarry from Roşiuţa on several undrained lakes. It slid until it threatened ND67, and the traffic to and from Târgu Jiu had to be detoured (Motru-Apa Neagră - Târgu Jiu).

The materials that make up the heaps of debris of the quarry from Roşiuţa are mainly clays and fluffy. Part of the water from the precipitations enters the body of the heap of debris, where, as a consequence of the reduced degree of permeability, its circulation is not possible, being absorbed by the clays that can take up a very large quantity. The bloating of the clay with water leads, on the one hand, to the drastic reduction of its mechanical resistance features, and, on the other hand, to the creation of a pressure in the pores, conferring the water a slightly ascending feature.

The muddy flows met in a natural environment, but with reduced dimensions, frequently occur at the edge of the heaps of debris Creep - the slow flow process It is recorded on the slopes formed of sand or sandy clays. It does not affect the stability of the slopes, only the forest vegetation. The trees lean in the direction or the directions of the movement, because of the root movement, together with the particles engaged in the movement, the forest gets the appearance of a "drunken forest". It occurs on the south-west slope of the Bujorăscu hill, as well

as isolated on the majority of the slopes located along the valleys.

5. Conclusions In our country, the interest for reintroducing the agricultural circuit of the degraded lands from current mining activities dates from 1968, numerous institutions from Bucureşti, Craiova, Petroşani and Cluj, drawing up large studies on this subject[7].

The emergency situations management is achieved through: - preventive measures; - urgent preventive intervention measures; - rehabilitation measures.

In order to reduce the problems caused by the mining industry, but also because of other productive and household activities, the following should be considered a priority: • The strict reduction of the acceptable limits for the exhaust gas releasing processes; • The prevention of the degradation of the lands and the forests; • The promotion of non-polluting technologies; • The assurance of the proper transportation and deposit of the waste and the debris within the landfills; • The planting (where possible) of the degraded lands; • The creation of a planted protection strip along ND 67, between the inhabited area and the industrial and landfill platform.

References 1. Ardeiu, M. Motru city and surroundings, Drobeta Turnu Severin, Editura Radical, 1999 2. Fodor, D., Baican, Gv. The impact of the mining industry on the environment, Deva, Editura Infomin, 2001 3. Huidu, E., Giurgiulescu, A. Mining monography from Oltenia, vol. III şi IV TârguJiu, Editura Măiastra, 2008 4. Lazăr, M., Dumitrescu, I. The human impact on the envrionment, Petroşani, Editura Universitas, 2006 5. Nistor, C., Achim, F. Considerations on the relief dynamics from the coal basin Motru, Simpozionul Naţional de Geografie, Bucureşti, 2001 6. Rotunjanu, I. The stability of slides and slopes, Deva, 2005 7. x x x Project documentation and geotechnical studies from ICSITPML-Craiova.

8. x x x Study regarding the development of external dumps Valea Ştiucani, Valea Rogoazelor, Valea Bujorăscu Mic, for raising the deoposit volume compared to initial project- ICSITPML Craiova, Simbol 705-44 Revista Minelor - Mining Revue no. 1 / 2012

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SEISMIC RESPONSE BY SPECTRAL ANALYSIS OF THE SYSTEM ROCK - UNDERGROUND CONSTRUCTION (TUNNEL) Eng. William Flavy RITZIU Abstract: Analysis of seismic response of structures buried by spectral analysis, is one of the most effective method for verifying the earthquake resistance of these buildings, with major impact for the population. Concrete railway tunnel, in this case study is located at an altitude of 1000 meters, is 128 m in length, earth coverage of 26.17 m. The cross section is horseshoe shaped, concrete and the soffit is molon protection. The present research uses a computer model consisting of two-dimensional finite element flat deformation state. Spectral analysis was used to design software SAP2000V14.

Key words: underground construction, earthquakes, spectral analysis, tunnel, static load, its dynamic response.

1. Introduction One of the most important activities related to underground construction safety, construction is to determine the behavior of seismic shock acceleration. This activity is coordinated Romania and P100-2006 according to norm established procedures and core values to be considered. You do not have spared no effort to achieve earthquake resistant civil engineering. In addition to reviewing the considerations static loads and their dynamic response, the calculation to seismic action was considered in two ways, as the spectrum of design and form of accelerograms. We also have to consider zoning the territory of Romania in terms of peak values of ground acceleration for earthquakes having IMR design (the average recurrence) 100 years (P100-2006) and the Romanian territory in terms of zoning period control (corner) Tc response spectrum (P100-2006).

Tc = 1.0 sec and ag = 0.28 g. Behavior factor q was determined based on P100-2006 and on the structure regularity account. For the behavior factor q, it was considered the structure with only two

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walls, thus Îą0/Îą1 = 1.0 was chosen for studying tunnel value q = 3.

This paper emphasizes the results of behaviorenvironment tunnel system to seismic accelerations, so that they last only review findings static loading and its dynamic response of the tunnel. Diagrams were also reproduced the most significant.

2. The calculation model The calculation model consists of two-dimensional finite elements in a state of plane deformation (Mesta 1997, Fierbinteanu 1989) The calculation has been considered an area of 26.17 m above and the rest around 5 tunnel diameters.

Generated by the model size (63x56m) ensures the elimination of the consequences of disturbances created by the cinematic shape.

Therefore the vertical sides of rigid links were placed horizontally and in vertical elastic links.

At the bottom of the rigid link model were introduced in the vertical direction.

To increase the accuracy of the model has increased the number of vertical and horizontal elements resulting in 1866 nodes and 3613 degrees of freedom (equations).

Details: n = node E = element

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Vibration characteristics are determined by the modulus of elasticity (kN/m2), Poisson ratio and specific gravity down concrete tunnel (B150), moloane concrete foundation (B75).

3. Considerations on static loading The values of any size coming from symmetrical loads are also symmetrical.

It is considered the maximum vertical direction, amounting to 5.3 cm as a result of their weight and 0.02 cm the effect of 20% of the convoy.

Horizontal displacement, the value is 0.73 cm (for weight) is 14% of vertical movement.

Unified efforts as both S11 and S22 in the direction of their maximum values in the tunnel elements. For its own weight load peaks are in different areas of the tunnel, while the convoy loaded with the maximum weight is in the slab.

1-1 are maximum efforts towards the different sections - the middle slab to load its own weight and the upper slab for convoy. However, the overall model, efforts are in the slab S11 for both types of loads. 1-1 maximum effort for the convoy is about 11% of maximum effort for 1-1 own weight.

Maximum efforts towards 2-2 are placed on the inside of the tunnel or the distance between walls is maximum or corner of the slab. Convoy intake is different in the two levels, namely 3% is almost to the distance between the walls is high and about 12% at the upper slab.

4. Comments on its dynamic response Fundamental mode (T1 = 0.407 s) located between the structure with rigid behavior. Type vibration vector is vertical translation.

Module two (T2 = 0.326 s) is a horizontal vibration which causes the 84% modal mass. Its period 2 value is 20% lower than the value of the fundamental period, while the proportion of the modal mass is driven higher by 27%.

Module three (T3 = 0.282 s) is the amount of torsion and its period is 31% lower than the fundamental mode. It is considered that the movements of ambient rock system - tunnel are very orderly and a drive assembly.

5. Spectral response The study seeks seismic response by spectral analysis. Spectrum is the spectrum of design used in normative P100-2006, according to seismic zone is located in the tunnel.

Given the dynamic sensitivity of the structure, the spectrum was considered in three cases of application, namely: 1) vertically, (2) horizontally and (3) to 450.

The figures below are maximum and minimum consistent efforts if the action spectrum for both the vertical direction across the field-structure and the structure. Mechanical values of the spectral response characteristic are summarized in the same manner in the following tables.

Table 3. Sizes mechanical characteristic points spectral response / Vertical spectrum

Node Movement Unitary effort kN/m2 number (m) Land area - middle 1809 Vertical S11 11.6 S22 248.8 0.042 Land surface Left 1794 Vertical S11 155.3 S22 46.5 (extreme points) Right 1822 0.01 S11 211.3 S22 69.7 Tunnel - Key 1739 Vertical S11 31.3 S22 500.2 soffit 0.0266 Tunnel - walls to Left 1707 Vertical S11 22.8 S22 1377.7 the maximum Right 1771 0.026 S11 23.5 S22 1377.0 Tunnel - vault Left 1681 Vertical S11 112.1 S22 679.5 birth (interior) Right 1684 0.0261 S11 113.1 S22 680.9 Tunnel - mid-slab 1648 Vertical S11 728.5 S22 34.1 0.0259 Tunnel â&#x20AC;&#x201C; slab edge Left 1643 Vertical S11 205.0 S22 797.7 (corner) Right 1653 0.026 S11 205.2 S22 802.4 Tunnel - extreme Left 972 Vertical S11 150.1 S22 623.1 Foundation Right 990 0.026 S11 148.2 S22 483.4 Node position

Fig.1 Spectral response charts where it is placed on the vertical direction Table 2. Values of mechanical assembly - spectral response / vertical spectrum.

Mechanical size Maximum Displacement (m)

Unified Effort kN/m2

Vertical direction Horizontal direction S11 Max Min S22 Max Min S12 Max Min

Value Position 0,042 In the middle of the land surface model 0,01 Land surface 773,5 2,7 1452,3 2,4 727,2 0,0

The tunnel - the middle slab In several areas - Tunnel + Ground The tunnel - the side walls The lateral limits below ground tunnel The tunnel - the side walls The tunnel at the bottom of the shaft

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Fig. 2 Spectral response graphs if the spectrum is inserted horizontally Table 4. Values of mechanical assembly - spectral response / horizontal spectrum Mechanical size

Value

Position

Vertical 0.0003 land surface Maximum direction Displacement Horizontal 0.0086 land surface in the middle of (m) direction the model S11 Max 192.3 slab over the tunnel Min 0.2 land surface in the middle of the model Unified S22 Max 83.8 land surface - to the extreme Effort kN/m2 Min 0.0 field S12 Max 66.0 land surface â&#x20AC;&#x201C; Extreme field Min 0.0

Table 5. Mechanical sizes characteristic points response spectral / horizontal spectrum

Node Movement Unitary effort kN/m2 number (m) Land - means 1809 Horizontal S11 0.3 S22 14.2 0.008 land surface Left 1794 Horizontal S11 62.6 S22 59.5 0.0 (extreme points) Right 1822 S11 73.3 S22 48.8 Vertical 0.001 Key tunnel soffit 1739 Horizontal S11 5.76 S22 32.6 0.0083 tunnel - the wall at Left 1707 Horizontal S11 1.0 S22 13.9 maximum distance Right 1771 0.0082 S11 1.0 S22 13.9 tunnel - the birth Left 1681 Horizontal S11 23.5 S22 11.5 of the vault Right 1684 0.0083 S11 23.7 S22 11.6 (interior) tunnel - the middle 1648 Horizontal S11 11.3 S22 2.3 slab 0.0083 tunnel - slab edge Left 1643 Horizontal S11 126.9 S22 43.9 (corner) Right 1653 0.0080 S11 126.7 S22 44.3 tunnel - extreme Left 972 Horizontal S11 40.1 S22 3.6 Foundation Right 990 0.0083 S11 40.1 S22 3.6 Node position

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Fig. 3 Spectral response graphs if the spectrum is introduced at 450 Table 6. Values of mechanical assembly - response spectral / spectrum at 450 Mechanical size Vertical Maximum direction Displacement Horizontal (m) direction S11 Max Min S22 Max Unified Min Effort 2 kN/m S12 Max Min

Value

Position

0.03

land surface in the middle of the model 0.0084 land surface - extremities 548.7 2.0 1026.9 2.4

tunnel - mid-slab in several areas of land tunnel - the side walls field lateral limits under tunnel 514.3 tunnel - the side walls 0.0 field at the bottom of the shaft

Tabel 7. Mechanical sizes characteristic points response spectral / spectrum at 450

Node Movement Unitary effort kN/m2 number (m) Land - means 1809 V 0.0298 S11 8.17 S22 176.2 H 0.062 land surface Left 1794 V 0.0071 S11 118.4 S22 53.4 (extreme points) Right 1822 S11 158.1 S22 58.9 Key tunnel soffit 1739 V 0.0188 S11 22.1 S22 354.4 H 0.0083 tunnel - the wall at Left 1707 V 0.0185 S11 39.7 S22 974.2 maximum distance Right 1771 H 0.0058 S11 42.7 S22 973.6 tunnel - the birth Left 1681 V 0.0184 S11 81.1 S22 480.5 of the vault Right 1684 H 0.0058 S11 81.8 S22 481.4 (interior) tunnel - the middle 1648 V 0.0183 S11 512.3 S22 24.2 slab H 0.0059 tunnel - slab edge Left 1643 V 0.0184 S11 171.3 S22 567.0 (corner) Right 1653 H 0.0058 S11 171.4 S22 566.7 tunnel - extreme Left 972 V 0.0184 S11 110.2 S22 341.6 Foundation Right 990 H 0.0083 S11 110.2 S22 341.8 Node position

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Table 8. Maximum and minimum values of mechanical quantities of spectral response for the three load cases Vertical Horizontal Spectrum Mechanical size spectrum spectrum at 450 the maximum vertical direction 0.042 0.003 0.030 movement(m) horizontal direction 0.01 0.0088 0.0084 S11 Max 548.7 192.3 548.7 In tunnel slab corners Min 2.7 0.2 2.0 S22 Max 1452.3 83.8 1026.9 Unified effort In tunnel In tunnel kN/m2 lateral walls lateral walls Min 2.4 0.0 2.4 S12 Max 727.2 66.0 514.3 Min 0.0 0.0 0.0

6. Conclusions on the response spectrum loading structure design As expected design load spectrum in the vertical direction leads to the highest values of spectral response.

Maximum values are field trips to the top of it. Maximum values are consistent efforts in concrete structure on the side walls of the tunnel.

And the slab is applied to values approaching the maximum.

Travel, spectral response spectral maximum vertical load is about 14 times higher than the maximum spectral response spectral horizontal loading.

Nodal displacements from 0.042 to 0.003 (m) To work unit spectral response spectral maximum vertical load is about 7.5 times higher than the maximum spectral response spectral horizontal loading.

Efforts uniform spectral lines 1452.3 to 192.3 (kN/m2) One can say that the response displacement spectral type is 2 times more sensitive than single response type effort.

The maximum spectral vertical - 4.2 cm - is under static displacement under its own weight 5.3 cm - representing about 80% of it. The

maximum spectral horizontal - 1.0 cm - is about 37% higher than static maximum horizontal displacement - 0.73 cm.

References 1. Andersen, L., Hausgaard Lyngs, J. Shortcomings of the Winkler Model in the Assessment of Sectioned Tunnels under Seismic Loading, DCE Technical Memorandum No. 10, Aalborg University, 2009 2. Anderson, D.G., Richart, F.E. Jr. Effects of Straining on Shear Modulus of Clays, Journal of Geotechnical Engineering, Division ASCE, pp.127(1976).

3. Bilotta, E., Lanzano, G., Gianpiero, R., ş.a.

Pseudostatic and Dynamic Analyses of Tunnels in Transversal and Longitudinal Directions, 4th International Conference on Earthquake Geotechnical Engineering, Thessaloniki, Greece (2007).

4. Hardin, B.O., Drnevich, V.P. Shear Modulus and Damping in Soils: Design Equations and Curves, Proceedings of ASCE: Journal of the Soil Mechanics and Foundations Division, Vol.98 (SM7), pp.667–692, 1972 5. Ritziu, W.F. Calculul incarcarilor statice si raspunsul dinamic propriu al unei constructii subterane, Annals of the University of Petroșani, Mining Engineering, 2011.

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LANDSLIDES AND SLOPE COLLAPSE IN THE ACUMULATION LAKE ZONE GURA APELOR Nicolae PĂUNESCU* Abstract Impression of total inner calm that gives us rigid crust of the earth is misleading.

Research area aims to identify and carry out works to strengthen the movement of portions consisting of rocks on a sloping surface which has product in areas where the soil is composed of different types of clays, with property to swell when soaked in water or result from the operations of freeze and thaw settlement results in the geological field.

Gura Apelor dam, with a tourist area, could lead to major material damage and human losses due to sliding Frequently producers without taking action.

The Râul Mare valley respectively of the Lapusnicul Mare about 1.000 m deep in the Borascu erosion surface bridges, separates the Retezat from the Tarcu and Godeanu mountains to East, Bărbat River and Pilugu River is the true limit of the massive, separating it Tulisa Mountains.

Fig.1 Separation of rock on the road to the dam Gura Apelor

1. Introduction This paper is developed based on the research done in the field to determine the risks of the landslides hazards from the accumulation lake zone Gura Apelor from the Retezat Râul Mare and adjacent fields.

2. Geographic location The studied perimeter is situated in the Southern Carpathians, in Hunedoara County, specifically within the confines of the village Hateg. At the end of a difficult road is mountainous with steep slopes including high walls of rock, about 47 km away from the city of Hunedoara Hateg, Gura Apelor is huge dam and 400 km by rail from the capital. ____________________________________ * Ph.D. stud, eng.- University of Petroşani

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Fig.2 Location of the studied perimeter overview of the dam during emptying Gura Apelor

3. The Climate In the Retezat mountains: you can’t find weather stations, the climate is determined by interpolating of the data’s obtained from weather stations Parang, Petrosani and Hunedoara.

The massif is located in the path of the west and south-western air masses. At over 2.000m altitude the average annual air temperature is about -2o, -4o C. Toward the altitudes of 1.400- 1.500 m, the mean air temperature are reaching the 2o, -4o C. In the hottest month, July the average air temperature is about 6o C on the highest peaks and about 8o-10o C starting at the upper limit of the forest towards the foot of the mountain. In the

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coldest month, January, to over 2.000m the mean air temperature is about -10o C and from the upper limit of the forest it increases to -8o, -6o C. 4. Geological conditions In terms of geological the area is complex because of so many tectonic units but also of so many types of rocks (sedimentary, igneous, and metamorphic) that exist. As shown in the geological map (fig.3), in the area is distinguished “The lower Danube units”. These are made of polimetamorphic formations crossed by granite massive and formations mildly metamorphosed due to pre-carboniferous Paleozoic era.

- The unit of nutmeg is composed of crystalline schists of the formations of Rausor (milon, biotite) and nutmeg.

- The unit of Petreanu with polimetamorphic formation of Bodu crossed by Petreanu gneisses and by the Stone Peak (Varful Pietrei) granite covered of Devonian formation mildly metamorphosed by Vidra.

- Followed then by Mesozoic permo sedimentary blanket, the lower Danube, with limestone, sandstones, clays and many others.

- Upper Danube units are consisted of sedimentary rocks, sometimes mildly metamorphosed and crystalline rocks (gneiss, amphibolites).

In the units are different: - The Poiana Marului Unit, with formation of Zeicani - green shale and formation Lăpuşnic quartz and graphite mudstone,sandstone, microconglomerates, limestone.

- The rock from the dam site of foundation contains: hard granitic rocks, compact and less permeable, in the center area (the rocky bed of the river) and on the left side.

5. The tectonic of the study area The lower Danube units are under the sign of two major elements: a) the slope from SE to NW of Rausor formation by the Retezat-Parang unit rocks along a line that exist on the right side of the Râul Mare, passing then to NE in the Rausor valleys, City and Nutmeg with the EW direction. The plan of subduction is considered overflowed age. b) The Râul Mare fissure system that separates between them the lower Danube units of Petreanu and Nutmeg with predominant NE-SW directions and falls to SE. The fissures do not affect the Mesozoic deposits but are covered both the northern and south end of the Alpine tectonic plan from the base of the upper Danube. This system of faults can be alpine foreland, sinalpine, but surely over thrust above the upper Danube.

Fig.3 Geological map of the dam region Gura Apelor and legend.

In these units we can speak about: - The unit of Retezat-Parang that has crystalline schists type Dragsan and granite from Retezat.

6. Hydrological and hydrogeological data Retezat Mountains are characterized by a dense network of rivers, with a rich and permanent flow.

The most important watercourse is the Râul Mare with a pool of 894 km2 and a length of 65, 8 km.

The area is found as water infiltration and şiroiri dripping in rock crevices and on different sections that cross faults, are streams of water as flows şiroiri and springs fed from the slopes or the lake, popular with debts of about 3 to 5 l / s The crystalline shale, water infiltration are reduced debt, they usually appeared on the faces of

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cracking dripping as weak, and very rarely Ĺ&#x;iroiri form of springs.

The presence of infiltration water in crystalline shale table caused an alteration and degradation time of intense tectonizate rocks.

Hydrologic point of view based on some mapping in natural openings( streams, torrents, wetting) and depth( drilling, wells, galleries) to achieve a hydrogeological model of the dam were determined the following characteristics: the groundwater lever, permeability, water absorption, water mineralization, and consumption of solid materials necessary sealing the rocks.

The Piezometers has noted two types of aquifers, namely: an aquifer stuck on the slopes, fracture type, irregular in shape, with depths ranging between 5 and 35m and an aquifer stuck in a riverbed, the alluvial layer, at the average depth of 2m.

7. Movements of rocks and erosion processes Slips affect units of mountainous terrain, is widespread in the Gura Apelor lake.

Fig. 5 Landslide in the river catchment area Tomeasa River Ses.

In these mountains of the dam, slopes composed of crystalline schists and volcanic rocks are affected by the collapse of rock and rolling pulse drop accompanied by the formation of different-sized debris.

Fig. 6 Slips and dislocations of granitic gneiss and clay altered, from the River Ses plain

Fig. 4 Overview of the Ses River after emptying the dam Gura Apelor

Under favorable conditions of humidity, with rain and long sharp melting snow layers, are many reactivation of old landslides threatening access roads in the area and new ones appear.

Slips affects the overall dam slope, separated into several compartments with different dynamics.

Sometimes they crossed valleys forming natural dams that pose a threat to downstream settlements and land, as was the catastrophe of 1999 in the colony, where there were significant material damage and human lives in Gura Apelor dam, for the cause of uniting natural dam on a creek.

Therefore, the first consideration for such training is draining dams and dam removal water obstacle course.

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Change in time of rainfall and hydrological regime of the hillsides, will have a direct impact on terrain modeling, and the trend of increase in temperature causes some changes in plant blankets.

Fig. 7 Ruins and wastelands from altered shale

Rock falls are more numerous during periods of frequent alternations of freezing and thawing as spring. These processes are a danger to the road that crosses the mountainous region, requiring special protection measures.

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Due to heavy rainfall and transport operators, the slopes of the R창ul Mare Retezat are affected by landslides, leading to displacement of soil and rock masses consistent slopes, along the plans, which are separated from the stable of the hillsides, the called sliding surfaces.

rainfall (235.1 mm, Cal, H2O in R창ul Mare hydrometric station), precipitated fallen in the range 8 to 11 July 1999.

Fig. 8 Recognition in the field of a landslide

Causes of landslides found in the study is excess water from melting snow slopes due to heavy rainfall,existing springs, land morphology, nature and structure of rocks.

The categories of items affected by the landslides and debris slope on R창ul Mare Retezat are: natural environment, built environment, population, material goods,etc.

Clues to the presence of some landslides are: steps bump on the slopes, waves on slopes areas, the existence of surface slopes in the form of language, areas with excess moisture on the slopes, springs or diffuse emerging water, especially in the lower half and the areas considered to be slipped.

There are also trees with trunks bent in different directions on slopes.

8. Floods and flood They are natural hazards affecting the network of settlements and land communication routes.

Floods are due to heavy rains, melting snow or a combination of two phenomena.

Flood wave propagation is strongly modified by anthropogenic activities.

The most important consequences have the floods with small basins, which are accompanied by a significant increase in a short time of the coarse sediment transport with a direct impact on settlements and ways of communication. Such a flood was produced on 11 July 1999, in the R창ul Mare basin, downstream of the dam Gura Apelor, from Retezat Mountains. The flood was associated with an increase of the hydro-geological and morphological processes. It had formed a temporary dam made of tree trunks and fragments of rock on a very small creek, which produced a debris flow that caused 13 casualties, 21 injured and destruction of communication lines for tens of kilometers. Flood was caused by high amounts of

9. Conclusions and recommendations Slips widely grown in relief units of the research area, being favored by the presence of clay and marly rocks, rain regime (which generates a steep slope humidity at certain times of year).

Formation characteristics from this area are very different both in terms of mineralogy and petrography, and also from the fracture system influenced point of view, probably, due to very high voltages metamorphism.

Addressing systemic problems of landslides in accumulation lake area can lead to Gura Apelor: - causes loss of stability and phenomena that occur in slopes; - possibility of progressive establishment of cause and effect links that will make a removable sliding material can be partially controlled.

Researches may lead gradually to the specification and detailing sliding and prevent disasters in the area of interest both in terms of tourism and in terms of electricity production.

It recommends a better correlation with the phenomena of building works of nature and design of new types of works, for the safe of the passers.

It should be established and ensures the functionality of the continuous information system, to alert local disaster.

It is necessary to draw up plans for defense against disasters and case studies for landslides in

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40

all bodies with duties and responsibilities on this line.

It is necessary to inform public opinion through the media on areas of potential risk, the imminent production landslides, their effects and the measures taken.

References 1. Arad V., Todorescu A. Rock and surface structure engineering, Editura Risoprint Cluj-Napoca 2006.

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2.

Center of Tehnical Information and Documentation Current processes to improve land stability. Synthesis studies 1975.

3. Păunescu, N. Contributions of property rock fill body of Gura Apelor Dam, the influence of seismic demands for the provision of possible damage. Research Report, Petroşani, 2009.

4. Surdeanu, V. Degraded lands geography Presa Universitară Clujeană, 1998.

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3D GEOTECHNICAL MODEL FOR THE NORTH-WEST AREA OF BUCHAREST Mihaela PAGNEJER* Abstract: The objective of this paper is to develop a 3D geotechnical model with three components: stratigraphic, lithologic and parametric with the purpose of underground works planning.

The model could be useful for the designing in adequate geotechnical conditions of underground works, underground transport (underpasses, subways, town tunnels).

This model extends on a surface of approximately 95 km2 and covers the Dâmboviţa and Colentina meadows, the Dâmboviţa - Colentina Interfluve, the high Field and the Colentina terraces.

The developped model goes as deep as 30 meters from the field surface and crosses several deposits of filling and Loess, Colentina and “intermediate deposits” Formations.

This model is based on data collected from 71 boreholes located North-West of Bucharest, within the railway ring.

Methodologically, this model was achieved by means of topo-probabilistic models (kriging).

Keywords: 3D geotechnical model, stratigraphic model, lithological model, parametric model, kriging 1. Introduction Safe underground works planning requires thorough geological knowledge of the formations affected by the future works. Besides the lithological, stratigraphic and structural data about the formations, detailed knowledge is needed also with regard to physico-mechanical characteristics of those formations.

The 3D geotechnical model presented in this paper has three components that describe the formations deposited on the first 30 meters, in the North-West part of the city: a stratigraphic one, a lithological one and a parametric one. (Fig. 1.1).

The 3D models were built starting from data collected from 71 geotechnical boreholes located in the researched area. Further, the 3D model was implemented according to topo-probabilistic models (kriging) that assess the level of uncertainty that describes the distribution of geotechnical parameters. The level of uncertainty is given by the observation points distribution and the parametric variability of formations. _____________________________ * Ph.D stud. eng. University of Bucureşti

2. General geomorphological framework of north-west Bucharest Nowadays, the bedrock of the city of Bucharest and of the area inside the railway ring is the object of abundant geotechnical, hydrogeological, environmental and urban research.

Thus, a synthesis of the lithostratigraphy and of the structure of the formations under research appears appropriate and necessary.

Bucharest is situated in the central part of the Vlasia Plain, which, in its turn is situated at the core of the Romanian Plain. The relief of the city is rather low and monotone, varying from 95 to 55 m high (Fig. 1). The rivers Colentina and Dambovita, with meadows as high as 85 m upstream and 55 m downstream and flowing NW-SE, divide the Bucharest Plain in three parts, relatively equal in terms of extent, but distinct in terms of age and lithological constitution (Enciu et al., 2008).

The Otopeni Field is situated on the left side of the river Colentina, within the forest Baneasa area and in its Western extent, towards the village of Straulesti. To the East, it continues up to the forests called Tunari, Boldu-Cretuleasa and Stefanesti. The Colentina Field lies between the rivers Colentina and Dambovita. The Cotroceni Field unfolds South of the meadow of the river Dambovita and, within the area of the municipality of Bucharest, has a high Field structure and three terraces formed by the river Argeş.

Fig. 1 Developing area of the 3D geotechnical model Revista Minelor - Mining Revue no. 1 / 2012

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Geologically, the area of the municipality of Bucharest and the surface inside the railway ring overlap a part of the Northern limit of the Moesic platform.

During the last evolution cycle, the Moesic platform (made up of a folded metamorphosed base and a sedimentary cover) was invaded by the waters of the Paratethys, which is known in Romanian literature as The Dacian Basin. During this last sedimentation cycle, formations belonging to the groups Olt-Vedea (Badenian-Sarmatian), Optaşi-Cartojani (Meotian-Pontian) and Bucharest (Pliocene-Quaternary) were accumulated (Pauliuc et al., 1979; Marinescu et al., 1998).

The Bucharest group contains nine formations : Merisani (lower Dacian), Calinesti (upper Dacian), Izvoarele (lower-middle Romanian), Frãteşti (upper Romanian – lower Pleistocene), Coconi (middle Pleistocene), Mostiştea (middle Pleistocene), “intermediary deposits”, Colentina and Loess Formation. The first three mentioned formations were defined by Papaianopol and Marinescu (1994), while the last six mentioned formations were defined by Liteanu (1952, 1953), Liteanu and Ghenea (1966), Alexeeva et al. (1983).

The geological formations intercepted in the 71 geotechnical boreholes of the data base are the following: • the Loess Formation; • the Colentina Formation; • the “intermediary deposits” Formation.

The “Intermediary deposits” Formation develops between the Mostiştea and the Colentina Formations and are represented by a clayey-silty formation, interbedded with one or two fine sands intercalations.

Clay sediments are made up of bluish-purple or grey clays and marls and loessoid deposits with calcite canalicula and concretions. Some of them are more or less sandy or have sand lenses. In some areas of the Capital, deposits have to some extent a lenticular structure.

The fauna of these deposits contains species belonging to the Viviparus, Melanopsis, Succinea genera and fragments of other gastropods.

The upper part of the Colentina Formation is made up of fine rust-colored sand that gradually changes its color into red-orange, with numerous organic debris, in the deeper parts of the formation (George Valsan, 1971). The deeper we go the more the granulosity increases, resulting into gravel. The whole sandbar is characterized by lensshaped sediments, enlarged towards the bed of the layer, regardless of whether the material is made up of fine sand with mica and gravel. All this evidence Revista Minelor - Mining Revue no. 1 / 2012

point to the fact that running water deposited the basic gravels in torrential regime. In a later period of maturity, they brought over small lens-shaped sands. Gravels are made up of quartzite, micaschist, sandstone, gneiss and jasper fragments.

Mammal fossil fauna includes Elephas primigenius sibiricus, Elephas antiquus, Cervus euryceros, Cervus megaceros, Bos priscus, Bos primigenius, Rhinoceros tichorhinus, Canis lupus, Hyaena crocuta.

The thickness of the Colentina Formation deposits varies according to the capability of the streams, which increases from Colentina (3-5 m), to Dâmboviţa (3-7 m) and Argeş (5-7 m).

The Loess Formation is made up of a sequence of 1-5 extended and continuous loess layers, separated by buried paleosoils (Enciu et al., 2008). The thickness of the layers varies from 1-2 m to almost 30 m. Loess clay deposits are lithologically specified by the granulometric variation of their components: clays, silt and fine sands.

These deposits are shaped as lenticular agglomerates, more or less clayish, with clacareous and mangano-ferruginous separations shaped as canalicula, concretions with frequent sand lenses.

The color of these deposits varies from yellowreddish to blueish-purple and gray; the sequence of colors is extremely irregular. This means that the sedimentation conditions also vary: in wind regime and perhaps, locally, in swamps, abandoned stream branches, etc.

Literature data points to the fact that loess is a wind deposit specific to cold periods, with more active air circulation; the fossil soils were formed during rather temperate-warm periods, rich in precipitation.

As far as the structure of the formations is concerned, in 1989 (Visarion et al.) complete the synthesis of structural elements on the whole Moesic Platform, based on geophysical investigations that reveal the existence of two systems of faults in the Capital area, namely NW and ENE-WSW (Fig. 2).

The map shows that apart from the majority of W-E faults, there exists a newer generation of faults, namely the NNE-SSW ones. Among them, the one that crosses Bucharest from South to North, through the East, is noteworthy, as well as some intracrustal earthquake epicentres situated in the North, close to the Chitila flexure (names so by Sãndulescu, 1984).

The explanation of faulting and of earthquake generation is provided by the platform being led into the subduction process towards the North, under the Carpathian Orogen.

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•

3. The database for the 3D geotechnical model for north – west Bucharest The 3D geotechnical model for North – West Bucharest was based on data collected from 71 geotechnical boreholes (Fig. 1) from which were taken 723 samples, for which were made 5400 determinations of physico-mechanical parameters.

The stratigraphic, lithological and parametric informations have been structured in a ROCKWORKS type of interactive database. The application ROCKWORKS is based on an ACCESS type of application to which was added a powerful tool for 3D zoning.

The data stored in the ACCESS database, created with the manager files for boreholes, can be exported to ASCII, DBF and EXCEL files.

To select the necessary data for the creation of the 3D geotechnical model for North – West Bucharest was made an application in Visual Basic (Fig. 3); this application enables the following actions: • first, it retrieves data from EXCEL files exported from the ACCESS base of ROCKWORKS package;

•

second, it filters the data using selection criteria such as: spatial, stratigraphic, lithologic and parametric; third, it saves selected data in ASCII files compatible with software used for zoning physico-mechanical parameters.

Fig. 2 Structural sketch of the Moesic Platform (Visarion et al., 1989)

1 2 3 4 5

6

7

Fig. 3 Application for data selection in view of creating the 3D geotechnical model

4. The method of calculation used for carrying out the geotechnical model The achievement of the 3D geotechnical model is based on topo-probabilistic methods of interpolation between alphanumeric values (lithology, stratigraphy) and numeric values (physico-mechanical parameters of rocks) obtained from a network of observation points with irregular distribution (the 71 boreholes located in the researched area). To this effect, I used two specific methods: • indicator kriging for alphanumeric variables;

•

punctual kringing (ordinary/universal) for numeric variables.

The application of kriging in the two variants was preceded by an analysis of primary data regarding the following: • the normality of distribution for the numeric values; • the stationarity of spatial distribution for the numeric values; • the anisotropy analysis for the alphanumeric and numeric values.

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It has been necessary to normalize and to eliminate regional trends of polynomial type (level two) for the oedometric modulus.

The anisotropy analysis was realized using as the main tool semivariogram:

()

γ d =

N (d ) 1 (vi − v j )2 ∑ 2 ⋅ N (d ) (i , j ) dij =d

where:

()

N d – the number of values pairs situated at d distance;

d – the oriented distance between the points i and j where the vi , v j values are determined;

vi , v j – the values measured in the points i and j .

The estimation of values and errors of the geotechnical model is based on minimizing the variance of the estimation errors synthesized in kriging systems: a) for ordinary kriging: ⎧ n ~ ~ ⎪⎪ ∑ w i ⋅ γ ij + μ = γ i 0 , ∀ i = 1, 2 , … , n j =1 ⎨ n ⎪ wi = 1 ∑ ⎪⎩ i =1

b) for universal kriging: k ⎧ n ~ ⎪⎪ ∑ w j ⋅ γ ij + ∑ μ l ⋅ f l ( p i ) = γ i 0 , i = 1, 2 , … , n j =1 l =1 ⎨ n ⎪ w i ⋅ f l ( p i ) = f l ( p 0 ), l = 1, 2 , … , k ∑ ⎪⎩ i =1

where: γ~ij - the value of variogram for the pair of values

vi , v j situated at distance d ij ; wi - the weight of vi values;

μ - Lagrange’s parameter;

f l - the regional trend function in the pi observation points; ( i = 1,2,..., n ); n - the number of observation points.

The error estimation of the 3D geotechnical model was realized for an assumed risk α = 5% using the relation: ε ( x0 , y0 , α ) = ±2 ⋅ σ~R The kriging allows to optimize the monitoring network by the fictive point method that uses the variogram model of the structure (model that incorporates the anisotropy parameters).

The calculation of anisotropy parameters (orientation for ellipsoid of anisotropy θ and anisotropy ratio η =

R ) is done using the surface r

variogram for each component of the 3D model (stratigraphic surfaces elevation, lithological type, plasticity index etc).

On the basis of the maximum permissible errors, the monitoring network is improved by filling it with additional investigation points. This ensures the accuracy requested by underground works planning.

5. 3D geotechnical model of the formations in the north-western area of Bucharest The geotechnical model presented in this paper extends on a 95 km2 area in the North-West part of Bucharest. It was built on the basis of 5,400 values of physical-mechanical parameters, determined on samples collected from the 71 boreholes (Fig. 1).

The three components of the 3D geotechnical model are the following: stratigraphic model, lithologic model and parametrical model.

The geometrical characteristics (features) of the interpolation grid of the stratigraphic, lithological and parametric model (Fig. 4) are: Δx = 50m , Δy = 50m and Δz = 1m where Δx, Δy, Δz represent the distances between the interpolation grid nodes on Ox (West-East), Oy (North-South) and Oz (elevation) direction.

z

The estimated value is calculated as follows: n

N

v *p0 = ∑ wi ⋅ vi

Δx

i =1

The minimum variance of error estimation has two calculations: a) for ordinary kriging: σ~ R2 =

n

∑

i =1

w i ⋅ γ~i 0 + μ

W

Δz

E

O Δy

x

S y

b) for universal kriging: n

k

i =1

j =1

σ~R2 = ∑ wi ⋅ γ~i 0 + ∑ μ j ⋅ f j ( p0 )

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Fig. 4 Geometrical characteristics of the interpolation grid

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5.1 The stratigraphic model The stratigraphic units of the model (from the surface to depth) are: the Loess Formation, the Colentina Formation and the “intermediary deposits” Formation: • the Loess Formation has maximum thickness in the high Field but is missing into the meadows of the two rivers; • the Colentina Formation is present almost everywhere in the researched area, the thickness of the horizon being variable; it is missing in some drillings in the South-West and extreme North-West of the researched area; • the “intermediary deposits” Formation has a relatively uniform disposition; there are some boreholes which did not detect this formation.

Aditionally to these three stratigraphic units, there is a horizon of filling material derived from building materials from demolations.

The average thicknesses of the four units belonging to the stratigraphic model (Table 1) indicate the presence of filling materials and loess deposits, which are less recomended for underground works, not exceeding 6 m deep.

Deeper than 6m, the prevailing formation is the Colentina one, with better bearing capacity properties, providing stability to the foundation works or underground works, but only if the inflow of underground water is dealt with approapriately.

Table 1 Average thickness and volume of stratigraphic units detected in the 71 boreholes

Formation Filling material Loess formation Colentina formation “Intermediary deposits” formation

Average thickness [m] 0,95 5,00 7,16 17,90

Significant variations of these units limits, which appear at local scale, are emphasized by the detailed 3D models prepared on this purpose.

The 3D stratigraphic model (Fig. 5) allows for a detailed description of the morphology of the separation surfaces between the identified stratigraphic units. The 3D stratigraphic model can be sectioned on any part of the work holding horizontal planes, at different elevations (e.g. map

Volume *107 [m3] 9 48 68 170

at +78 m – Fig. 6) or vertical planes (e.g. SW-NW section – Fig. 7). This allows to accurately determin the formations that are present at the base level and in the side walls of the excavations.

The stratigraphic model can be easily updated for already planned underground works by simply introducing the data derived from the supplementary boreholes into the general data base.

NE

SV

Fig. 5 3D stratigraphic model

SV

Dambovita

Fig. 6 Stratigraphic map at the level +78m

NE

Fig. 7 SW-NE section through the 3D stratigraphic model Revista Minelor - Mining Revue no. 1 / 2012

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categories: clayey silty sand (NPA), sandy clayey silt (PAN), vegetal soil (PVEG), filling material (U).

The weights of lithological types for each geomorphological unit were evaluated on the basis of nominal histograms and ternary diagrams (e.g. the high Field; Fig. 8 and Fig. 9) as well as the comparative analysis within the researched geomorphological units (e.g. the Dâmboviţa and Colentina river meadows - Fig.10).

5.2. The lithological model The 3D lithological model was realized starting from the lithological analysis of all the geomorphological units existing in the researched area: the meadows of the rivers Dâmboviţa and Colentina, the high Field, the Dâmboviţa Colentina Interfluve, the Colentina terraces.

The lithological variety of the researched area is represented by all lithological types in the ternary diagram together with four supplementary

Dâmboviţa Meadow 45 350

40

300

35

250

200

30

150

25 100

20

50

15

Colentina Meadow

5 0

100 0

Fig. 8 Nominal histogram for the lithology of formations in the high Field

Fig. 9 Ternary diagram of the deposits in the high Field, with the absolute frequency contur lines

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U

PNA

meadow

Fig. 10 Frequency distribution diagram for the lithological types in the meadows of the rivers Dâmboviţa and Colentina

PRAF

The main lithological features of the studied area are derived from the statistic analysis of the data (723 samples obtained from the 71 boreholes, for which 5400 determinations were carried out).

They are the following: • the lithological types in the meadows of the rivers Dâmboviţa and Colentina are similarly distributed (Fig.10); this even distribution is characterized by the sands prevalence (the most prominent one), by the silty clays and the gravels, as well as by a minimum of the silty fraction; • the lithological types in the high Field, the Dâmboviţa – Colentina Interfluve and the Colentina terraces have a similar distribution, characterized by the prevalence of the silty clay and clayey silt.

The quantification of the similarity with respect to the lithological distribution in the meadows of the rivers Dâmboviţa and Colentina, on one hand and in the high Field, the Dâmboviţa – Colentina Interfluve and the Colentina terraces, on the other hand, was realized on the basis of some lithological correlation coefficients above 0,85 in both cases.

All these results indicate the existence of two domains of lithological homogeneity: river meadow and terrace.

The significance of the lithological variability in the studied area (13 distinct lithological types)

S1

0 100

50

Nume gr upa

Pi

PVEG

P

NP

N

AP

A

0

10

has a complex spatial configuration marked by the characteristics of the stratigraphic model: • distinct lithological variation at the limit between the Loess Formation and Colentina Formation; • the continuous lithological variation at the limit between the Colentina Formation and the “intermediary deposits” Formation.

These general features are masked (hidden) in the model presented in this paper because of local variations and because of an uneven distribution of the investigation boreholes.

NE

SV

Fig. 11 3D lithological model

47

The above mentioned 3D lithological model (Fig. 11) permits the identification of some general lithological characteristics of the researched area: • on the high Field, Interfluve and the Colentina terraces, the clayey and the silty fractions are prevailing in the upper part of the Quaternary formations, as part of the Loess Formation; the clayey fraction, which exists even at deeper levels, can be found in the structure of the Colentina Formation and also in the structure of “intermediary deposits” Formation; • in the river meadow zones, the sandy fraction lies primarily at the surface, but it is present in the depth, too; the sand goes into the structure of the Colentina Formation and the “intermediary deposits” formation; • on a general background of content less then 20% of clay, at +67 m elevation the distribution in horizontal plane highlights the expansion of the “clayey deposits” horizon; • the distribution of the silty fraction maxima at +80 m on the high Field, Interfluve and the

SW

Colentina terraces points to the spatial expansion of the loess deposits in these geomorphological units; • at +73 m elevation, one can find in the Colentina terraces non-cohesive terrace deposits; in the high Field unit, the noncohesive deposits have a lens shape distribution.

Generally speaking, in the researched area there are lithological horizontal and vertical discontinuities, which are visible on a local scale.

This variability can be detailed in vertical sections (Fig. 12 and Fig. 13) and horizontal maps in the zones where underground works are being planned. The updating procedure of the lithological model is similar to the one applied to the stratigraphic model; this is due to the flexibility of the performed model, resulting from the topoprobabilistic models which I used.

Dâmboviţa

NE

Fig. 12 SW-NE section through the 3D lithological model

NE 90

80

70

60

Fig. 13 Variation of the sandy fraction in the vertical SW-NE section

5.3.The parametric model The aim of the 3D parametric model, based on the stratigraphic and the lithological model, is to provide the necessary parameters for underpasses, subways, bridges and hydrotechnical development in the North-Western part of Bucharest.

The main physico-mechanical parameters used to achieve the parametrical model are: plasticity index ( I P ), apparent density ( ρ ), porosity ( n ),

oedometric deformation modulus ( Eed ), internal

friction angle ( φ ), cohesion ( c ) and standard penetration test ( SPT ).

The achievement of the 3D parametric models for the seven physico-mechanical parameters (e.g.

3D parametrical model of plasticity index Fig. 14) was based on the values determined in the 71 geotechnical boreholes.

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NE

SW

Fig. 14 3D parametric model for the plasticity index

The seven 3D parametric models achieved in the studied area allow the identification of the following characteristics of the distribution values for the physico-mechanical parameters: • plasticity index is specific for clay layers (cohesive): its variation and especially the highest values overlap with the development areas of "intermediate clays". This information is extremely useful when designing retaining and dewatering work for civil objectives with one or more underground levels. This is so because the spatial extension of these deposits influence the choice of methods and technical processes.

• apparent density: this parameter’s extreme values highlights the areas where non-cohesive deposits have loose or medium state and the cohesive deposits have a low degree of consolidation, fundamentally influencing both the choice of the building foundation methods and the pumping system of the dewatering work.

• porosity: the maximum values of this parameter in cohesive or low cohesive deposits are an indicator of the low degree of consolidation and consequently of an area with low resistance parameters;

•

oedometric modulus: its variation is in perfect inverse correlation with the porosity variation, so the very large compressibility distribution areas almost overlap with the areas of extreme porosity; • friction angle: the variation of this parameter highlights the extreme areas – maximum ( φ > 25°), minimum ( φ <20º) respectively; • cohesion: the distribution of cohesion values correlates with the friction angle distribution, so the extreme areas of φ correspond to the minimum areas of cohesion; • standard penetration test: the distribution of SPT values is very useful in terms of its practical application, because it clearly highlights the "vulnerable" areas, whose exact interpretation must be correlated with the granulometric analysis.

Local variability of parameters can be detailed by crossing the seven parametrical models with vertical planes (e.g. SW sections with plasticity index and porosity variation - Fig. 15 and Fig. 16) and horizontal planes at the level of the foundation or at the underground mining work for subway.

Ip = 10 % Ip = 20 %

Ip = 35 %

90

80

70

60

Fig. 15 Variation of the plasticity index in the vertical SW-NE section

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NE

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n = 40 %

NE

90

80

70

60

Fig. 16 Variation of the porosity in the vertical SW-NE section

6. Conclusions The 3D geotechnical model achieved for the North-West area of Bucharest is a complex, multipurpose tool that provides, interactively, parametrical data required by underground mining work for the subway and hydrotechnical development.

The three components of the model presented in this paper – stratigraphic, lithological and parametric model – are based on the most flexible spatial interpolation methods (indicator kriging, ordinary and universal punctual kriging) and on a representative database (5400 values) for the Quaternary investigated formations.

The dominant feature of the spatial structures of the three models is the anisotropy, which was synthesized into an unique model (Fig. 17) for the investigated formations. This unique model was used, with acceptable errors, to assess the spatial distribution of the stratigraphic and lithological units and of the physical-mechanical parameters.

12o

Z N N

Z rz

R

E E Dâmboviţa

V V

r

V

S Z’

Z’ S

12o

Fig. 17 Anisotropy ellipsoid of Quaternary deposits from the North – West area of Bucharest

The unique anisotropy features set for the North-West area of Bucharest city are the following: • the direction of minimum continuity in "horizontal plan" N12oE; • the direction of maximum continuity in "horizontal plan" N78oW; • the "horizontal plan" of the anisotropy ellipsoid has the maximum slope direction N12oE and a 12o South slope; • the direction of maximum continuity in the vertical plane is, as in all layered sedimentary structures, the "horizontal" one, that in the specific studied case has a 12o slope to the South; • the anisotropy ratio in horizontal and vertical plane is 2.

The specific feature of the parametrical anisotropy ellipsoid for the cover formations in North-West area of Bucharest city is the low anisotropy ratio. This feature is connected to the heterogeneity of the sedimentary environment at local scale.

If for small distances the spatial distribution laws change, as the distances increase, due to the low magnitude of these changes, the distribution laws tend to be very similar. This spatial feature of the structures recommended the kriging as optimal evaluation method of the spatial distribution for the parametrical spatial models from the North-West area of Bucharest.

The general characteristics of spatial variability for the parametric structures in the city area are the following: • stationary variability for the extent of described model; • local variability, specific to distances smaller than 300 m, for all the physico-mechanical parameters; this characteristic involves a high density of observation points for detailed spatial analysis specific to geotechnical studies.

The estimation errors of the spatial parametric distribution are influenced mainly by the distances between the investigation boreholes. The local Revista Minelor - Mining Revue no. 1 / 2012

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heterogeneity allows for extrapolation only with the risk of uncontrolled errors; the interpolations introduce errors higher than 10% of the estimated value in the points placed at distances greater than 300 - 400 m from the points of direct investigation.

The 3D geotechnical model achieved for this research provides a software support that enables users to do the following: • to realize an unlimited number of sections and horizontal planes in the areas where underground works are planned, in order to detail the geotechnical conditions; • to be quickly updated with additional data that can be efficiently integrated in the database structure in order to reduce the estimation errors of the spatial distribution of the parameters.

References 1. Alexeeva, L., Andreescu, I. ş.a.

Correlation of the Pliocene and Lower Pleistocene Deposits în the Dacic and Euxinic Basins, Anuar IGR, 59, p. 143-151, Bucureşti, 1983 2. Bomboe, P., Mãrunţeanu, C. Engineering Geology, Vol. I, Bucureşti, 1986

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3. Florea, M. Rock Mechanics, Ed. Tehnicã, Bucureşti, 1980 4. Marinescu, Fl., Mãrunţeanu, C., Papaianopol, I., Popescu, Gh. Correlation of the Neogene Deposits în Romania, Inst.

Geol., Rom. Journ. Stratigr., 78, p 181-186, Bucureşti, 1998 5. Liteanu, E. The geology of Bucharest city, Com. Geol., Inst. Geol., E/1, p. 3-80, Bucureşti, 1952 6. Lãcãtuşu, R., Anastasiu, N., Popescu, M., Enciu, P. Bucharest city Geo-Atlas, p. 7-37, Ed. Estfalia, 2008 7. Pauliuc, S., Negoiţã, Fl., Darwische, M., Andreescu, I. The stratigraphy of the miocene deposits in the central sector of the Moesic Platform (Olt - Dâmboviţa), An. Univ. Buc., Geol., p 65-78, Bucureşti, 1979 8. Scrãdeanu, D., Popa, R. Applied geostatistics, Ed. Universitãţii din Bucureşti, 2001 9. Stãnciucu, M. In situ geotechnical investigations, Ed. Universitãţii din Bucureşti , 2010

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GEO-MECHANICAL CHARACTERIZATION OF THE A3 MOTORWAY ROUTE COMARNIC-PREDEAL IN THE CHOICE OF TUNNELING TECHNOLOGY EXECUTION WITH EXPLOSIVES Eng. Mihai BOLGAR Abstract: An efficient transport infrastructure, connected to the European transport network contributes to economic competitiveness, facilitates integration into the European economy and the realization of new domestic activities.

The current situation of the national transport system is characterized by a reduced number of highways..

1. Introduction Romania has established guidelines for communications of European and national interest

by National Spatial Plan, Section I “Ways of communication”. Among the projects to which participates in the development of trans-European transport, also belong the highway Bucharest – Brasov. Highway is designed with 4 sections: Bucharest – Moara Vlasiei, Moara Vlasiei – Ploiesti, Ploiesti – Comarnic and Comarnic – Predeal.

The road no.3 of the motorway is planned to run the route localities Comarnic – Sinaia – Busteni – Azuga – Predeal, on the Prahova river bed and in the immediate vicinity of the river, going through the Prahova Valley a distance of 36.2 km.

An analysis of rocks crossed by tunnels, in terms of characteristics used in the construction of the tunnels, by classification Romanian Geological Committee, led to the following conclusions highlight the possible groups of rocks: - Hard limestone marl and calcareous sandstones belonging compact layers of necomian Azuga or Sinaia, may be classified as very hard and hard rock, with a coefficient of rock strength of 6 - 9 and diffusion approx. 50%; - Marls of necomian can be classified as hard or semi-hard rocks, with coefficient of rock strength of 3 – 7 and diffusion approx. 30%; - Shale sandstone clay belonging of necomian layers of Sinaia can be classified as semi-hard rock, with a coefficient of rock strength 2 – 7 and diffusion approx. 20%.

In terms use of explosives, limiting factors are given for social and touristic objectives (Comarnic, Posada, Sinaia, Poiana Tapului, Busteni and Azuga), industrial facilities near the motorway and neighboring towns, not least the many protected areas included in the network NATURA 2000.

To carry out highway is necessary the execution of works both in size: at the land surface (excavation, leveling and grinding slopes), and also underground by executing of two tunnels near the village Azuga.

The works will take place on the land surface will run both the low strength rocks and the hard or semi-hard rocks. If are the soft rocks, cohesive or slightly cohesive work will be carried out with mechanized, and if are the hard or semi-hard rocks, blasting will be carried out with explosives.

Marl, clay shale belonging to the bar Comarnic Aptian layers, according Romanian Geological Committee classification, can be classified as semihard rock, with a strength factor of 3 to 5.

In order of blasting with explosives to be used the following techniques: - Mine holes, when blasting front height is up to 10 m; - Inclined boreholes, when the height of the works is more than 10 m.

Boreholes drilled inclined towards the vertical have the advantage of a more uniform distribution of the explosive in massive, a break and a more uniform slope. In order to achieve stable slopes, holes in the last row will have a smaller diameter than the rest of the device, the distance between them will be smaller and reduced loads.

Along the studied route in Prahova River defile areas, cross slope of mountain slope involve expensive building works of consolidation and a very large volume of excavation.

Taking into account the fact that the strip of land between the river and DN1 is furnished extensively with various constructions, or forest, that is necessary to study variants of solutions that minimize negative environmental impact that may have these excavations.

In this situation, we considered the embodiment of tunnels with separate section for each track, which allowed the better registration of the existing relief within the meaning of design, two tunnels from km 142+000, respectively km 144+307 which reduced both costs and negative environmental implications.

Adopting separate tunnel solution proved to be the best solution in terms of economic and relief.

To achieve tunnels will be observed the same sized specified in STATE 2924 concerning the bridges, but taking a higher safety space given the Revista Minelor - Mining Revue no. 1 / 2012

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free movement of road vehicles and the need for more intense ventilation.

Thus, the tunnel dimensions afferent of one sense of movement, motorway, dual-lane, emergency tape and pavement in 12 meters and the height is 8 meters.

Bedrock on the highway sector portion where I studied and considered it preferable to run tunnels, is the “layers of Sinaia” which are overall predominantly “flysch slate sandstone” with or without marls limestone, with intercalations of breccias and shale.

First tunnel proposed to run we meet near the locality Azuga and he has 2.30 km in length, in its

continuing, on the next slope, will be the next tunnel and he has 4.60 km in length.

To choose the optimal version of shot perforation, we performed a comparative study of the advance by firing two-stage drilling advancement or advance with one free surface.

Modeling was performed with the program Phase 2, such as making the modeling we can see the impact that has on the massive rock use of explosives.

Considering the rocks around the excavation and excavation dimensions, we conducted this study to observe the stress distribution around the work, for each type of advance in part.

2. Advance by two steps of excavation Highlighted tensions for if it used two stages of excavation are shown, graphically, as follows: - The first stage, excavation did not start:

- For stage 2, start first stage, excavation vault:

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- For stage 3, arch tunnel excavation is completed:

- For stage 4, starting excavation of second stage:

- To stage 5, the excavation is complete:

The interpretation of results for horizontal and vertical movements is follows: - Vertical and horizontal movements for stage 1:

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- Vertical and horizontal movements for stage 2:

- Vertical and horizontal movements for stage 3:

- Vertical and horizontal movements for stage 4:

- Vertical and horizontal movements for stage 5:

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Movements in all five stages are given in the following graphic:

3. Advance with one free surface Some as in case the excavation is done in two steps of execution was carried out and where the design is done by piercing shot with a free surface.

To finally make a comparison of two methods of advancing creates greater movement and higher tension into massive, if a single free surface, we conducted a Phase 2 modeling software

(finite element modeling), to see how the massive behave and what displacements occur in this case.

So, the way forward with smaller displacements and lower tension, will be the most appropriate from this point of view, because creating displacements on the outline of the work greater than allowed (red color), will affect the stability in terms of tunnel construction..

Thus, further, I present the results of horizontal and vertical displacements, obtained from modeling of tunnels that are believed to run with one free surface: - Phase 1 of execution, massive is unaffected:

- Phase 2 of execution, excavation begins:

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- Phase 3 of execution, excavation is completed:

Vertical and horizontal displacements are shown in the graph below:

4. Conclusions Following implementation modeling with finite element by program Phase 2, can notice a considerable difference between the two methods of advancing with the perforation shooting.

The difference is that for digging in one step the movements are sudden and large, and to advance in two steps displacements are much smaller, so the risk of cracks in the massive is much lower in this case.

An particular importance is the type of rock and section work, but the results show that for not to be influenced the stability of work, the most appropriate is that the perforation shooting of tunnel to be done in two steps.

References 1. Law 203 / 2003 regarding the development of the national and european transport network; 2. P.O.S. "Transport" 2007 - 2013

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3. Moldavian Technical University Open pit mining, Chişinău, 2007; 4. Fodor D. The use of explosives in industry, Editura Infomin, Deva, 1998; 5. Fodor D. Explosives engineering. Work materials and techniques.

Volume 2, Editura Namaste, Timişoara şi Editura Corvin, Deva, 2007; 6. Chirilă D. Tunnels, Editura Universitas, Petroşani 2005; 7. ECOTURISTICA Magazine – Turism electronic magazine No. 5, March 2007, Editura Asociaţiei Ecologie - Sport Turism 8. Ministerul Transportului – CNADNR Public acquisition file – consulting services regarding the giving documentation and assisting the authority in the process of forming the contract for the objective Bucureşti – Braşov highway, part Comarnic - Predeal; 9. SEARCH CORPORATION, S.C. IPTANA S.A. Geotechnical and feasibility studies.

10. http://www.roscience.com - PHASE 2